Document:

<PAGE>

                                                                    EXHIBIT 10.1

The following constitutes a fair and accurate English translation of the
ProFound Pharma A/S lease with the Science Park in Horsholm.

   /s/ Christian Hansen
----------------------------
Christian Hansen
Co-President, Pharmaceuticals

                                Lease Agreement

                              ProFound Pharma A/S

                              Re lease located at

                                 1 Agern Alle
                           Science Park in Horsholm
<PAGE>

                                       2

Between

The independent institution
The Science Park in Horsholm
(hereinafter referred to as Lessor)

and

ProFound Pharma A/S
1, Agern Alle
2970 Horsholm
(hereinafter referred to as Lessee)

the following lease agreement has been made

The lease
(S)1
The leased property is located at 1, Agern Alle and comprises gross floor space
of 2,441 m2, including shared space of 383 m2.  A storage room in the basement
of 40 m2 is also included in the lease.

The location and arrangement of the leased property is described in greater
detail in the attached plan. (Encl. 1).

Use
(S)2
The leased property shall only be used for research and development or
communication of results originating therefrom and in connection with a limited
amount of production.  The leased property shall not be used as an actual
production plant.

The use of the leased property shall furthermore comply with any rules in force
at any time for the Science Park in Horsholm. The regulations in force at the
time of entering the agreement are attached to this contract (Encl. 2).

Requirements of the authorities, etc.
(S)3
During the lease the Lessee guarantees that the leased property as well as the
use and operation thereof shall comply with the requirements stipulated at any
time by any authority, and the Lessor is relieved of any such responsibility in
that respect.

Furthermore, the Lessor shall ensure that the use of the leased property at any
time is in accordance with the liens and easements of the property.

Any measures relating to fire protection, renovation and interior arrangements
that may be required by the housing authorities, the Danish Working Environment
Authorities or other authorities as a
<PAGE>

                                       3

condition for the use of the leased property as contemplated by the Lessee shall
be made at the expense of the Lessee.

Responsibility of the Lessee
(S)4
The Lessee is under an obligation to indemnify, based on a neutral assessment,
the Lessor for any claim made against Lessor for any damage caused to the leased
property that is due to the Lessee's use of the leased property, including e.g.
damage caused to the buildings and the site and water table due to pollution.

Takeover
(S)5
The Lessee shall take over the lease as from 1 May 2000. However, the Lessee
shall take over a space in the basement of 483 m2 (robot room) as from 1 April
2000.

The leased property consists of a newly constructed building.

Lessee shall take possession of the property "as is," in the same condition as
when the leased property was inspected by the Lessee.  However, this does not
include hidden defects, in which case the Lessee shall notify the Lessor not
later than 14 days after the Lessee should have discovered any such defect
exercising usual due care, otherwise the right to claim the defect will be lost.

In connection with the transfer of possession, an official possession transfer
meeting shall be held with the participation of a representative of the Lessor
as well as the Lessee. As a result of the official possession transfer meeting a
report shall be made describing the condition of the leased property at the time
when possession of the leased property is transferred.

Maintenance
(S)6
The maintenance of the interior of the leased property, including maintenance,
repair and renovation of the flooring, furniture and equipment, locks, keys,
windows, water and gas outlets and taps, sanitary installations, lighting
fittings and electrical switches and any heating, freezing and fume cupboards is
the responsibility of the Lessee.

A share of the indoor cleaning, operation and maintenance, etc. of the joint
space of the property is the responsibility of the Lessee.

The exterior maintenance is the Lessor's responsibility.

Special installations established to be used by the Lessee for this leased
property, such as venting system, gases, water processing systems, lab
equipment, etc. shall be operated and maintained by the Lessee in accordance
with the directions issued by the Lessor.
<PAGE>

                                       4

The Lessee is obliged to inspect the leased property at least once every year
together with the Lessor and in connection with the inspection an agreement
shall be made as to the extent to which any repair or renovation shall be
carried out.

In case the Lessee does not meet its obligations with regard to maintenance the
Lessor shall be entitled to have the maintenance tasks carried out at the
expense of the Lessee, after having made a claim towards the Lessee, and given
Lessee a reasonable term to remedy the deficiency.

Changes to the Building
(S)7
The Lessee shall not make any changes to the building without having obtained
the Lessor's prior written consent.

Any changes to the building shall under any circumstances be made on the basis
of a project as usual and shall be carried out by authorized artisans and
furthermore be in accordance with the usual construction regulations and
official requirements, etc.

The size and payment of the rent
(S)8
The annual rent for the year 2000 amounts to DKK 3,010,225.00, corresponding to
a price per sq.m. of DKK 1,225.00 per year and DKK 500.00 per sq.m. per year for
the rooms in the basement, and is calculated in accordance with the lease
conditions applied by the Science Park. Value added tax is to be added to the
rent.

From 1 January 2001 the annual rent for the office and laboratory space will be
subject to an increase of DKK 70.00 per sq.m. plus indexation.

From 1 January 2002 the annual rent for the office and laboratory space will be
subject to a further increase of DKK 50.00 per sq.m. plus indexation.

The rent is calculated on the basis of a total of 2,481 m2.

The rent shall include taxes and public duties, etc. in respect of the property
as per 1 January 2000.

The rent shall be paid in advance for one month at a time in accordance with the
Lessor's instructions.

Regulation of Rent
(S)9
The rent applicable at any time is fixed every year on 1 January after the
assessment of the Board of the Science Park of the conditions. However, the rent
is subject to a maximum increase corresponding to the development of the net
price index from October to October.

If the net price index is no longer calculated, the rent regulation will be
based on a similar index.

In order to illustrate the consequences of the index regulation an example is
shown:
<PAGE>

                                       5

<TABLE>
<CAPTION>
Year            Low growth                                   High growth
--------------------------------------------------------------------------------------------------------------
                Index              Annual Rent               Index              Annual Rent
--------------------------------------------------------------------------------------------------------------
<S>           <C>       <C>        <C>                       <C>                 <C>
2000           100      DKK         3,010,225.00             100                 3,010,225.00
--------------------------------------------------------------------------------------------------------------
2001           102      DKK         3,244,716.90             104                 3,308,338.80
--------------------------------------------------------------------------------------------------------------
2002           104      DKK         3,369,207.90             108                 3,435,270.80
--------------------------------------------------------------------------------------------------------------
2003           106      DKK         3,436,592.06             112                 3,572,681.63
--------------------------------------------------------------------------------------------------------------
2004           108      DKK         3,505,323.90             117                 3,715,588.90
--------------------------------------------------------------------------------------------------------------
2005           110      DKK         3,575,430.38             122                 3,864,212.45
--------------------------------------------------------------------------------------------------------------
2006           113      DKK         3,646,938.98             127                 4,018,780.95
--------------------------------------------------------------------------------------------------------------
2007           115      DKK         3,719,877.76             132                 4,179,532.19
--------------------------------------------------------------------------------------------------------------
2008           117      DKK         3,794,275.32             137                 4,346,713.48
--------------------------------------------------------------------------------------------------------------
2009           120      DKK         3,870,160.83             142                 4,520,582.02
--------------------------------------------------------------------------------------------------------------
2010           122      DKK         3,947,564.04             148                 4,701,405.30
--------------------------------------------------------------------------------------------------------------
2011           124      DKK         4,026,515.32             154                 4,889,461.51
--------------------------------------------------------------------------------------------------------------
2012           127      DKK         4,107,045.63             160                 5,085,039.97
--------------------------------------------------------------------------------------------------------------
2013           129      DKK         4,189.186.54             167                 5,288,441.57
--------------------------------------------------------------------------------------------------------------
--------------------------------------------------------------------------------------------------------------
Low                                 2% per year
growth
--------------------------------------------------------------------------------------------------------------
High                                4% per year
growth
--------------------------------------------------------------------------------------------------------------
</TABLE>

In addition to the adjustment based on the net price index (and irrespective of
the Lessor not being entitled to terminate the lease) the rent may be subject to
adjustments in accordance with the lease legislation existing at any time, cf.
Sections 3-5 of the Danish Act on Business Leaseholds.

Taxes and Duties
(S)10
The Lessor may demand that the annual rent be adjusted in accordance with
changes in the taxes and duties levied in respect of the property of the Science
Park, including any additions or changes in new taxes and duties levied of any
kind.

Building taxes including service charge are shared according to the gross floor
space stipulated in this Lease Agreement. The share of the lease of the building
taxes and duties are calculated as the share of the gross floor space of the
total gross floor space of the Science Park.

Heating, Water, Electricity, etc.
(S)11
The Lessor shall supply the leased space with heating from the district heating
system of the Science Park.  The expenses for the heating shall be reimbursed by
the Lessee.

The Lessee shall pay for its heating consumption in accordance with a separate
meter.
<PAGE>

                                       6

In addition to the direct expenses for fuel, Lessee shall be responsible for its
share of all other expenses incurred in connection with the Lessor's supply to
the leased property of heating and hot water, including e.g. janitorial
expenses, water and electricity to run the heating system, administration,
technical inspection by an engineer, expenses for repair, preparation of heating
accounts and write off on the system.

In addition, the Lessee shall pay to the Lessor all expenses relative to the
water supply of the lease, including consumption tax and fixed duties, in
accordance with a meter.

The fiscal year for the water and heating supply is the calendar year.

The Lessor shall invoice the Lessee for the estimated share of the total
expenses of the leased property for the heating and water supply, and the Lessee
is obliged to pay these expenses monthly along with the rent.

As of the beginning of the lease, the estimated costs of providing water and
heating amounts to DKK 11,500.00 per month (exclusive of VAT).

The Lessee shall pay for its consumption of electricity directly to the
electricity supplying company according to a separate meter.

The Lessor shall not be responsible for the sufficiency or insufficiency of the
capacity of inlets, drains and outlets with regard to the needs of the Lessee.
Any additionally required inlet, drains and outlets are made by the Lessor at
the expense of the Lessee.

Specification of expenses due in addition to the rent
(S)12
The expenses that shall be paid by the Lessee in addition to the rent and that
are known at the time of entering into this agreement are specified below, see
also subsections 4 and 5 of Section 4 of the Danish Rent Act.

1.     Heating Expenses
       Estimated annual fuel expenses           DKK 78,000.00
       Estimated annual expenses included in
       the heating account for operation
       and maintenance of the heating
       system                                   DKK 30,000.00
                                                ---------------------

       Total estimated annual heating
       Expenses                                 DKK 108,000.00
                                                ---------------------

<PAGE>

                                       7

<TABLE>
<CAPTION>

<S>                                             <C>
2.     Expenses for water supply
       Total estimated annual expenses
       for water supply                         DKK 30,000.00
                                                -------------
</TABLE>

The above figures are budget figures, and the real expenses may vary from the
above.

Deposit
(S)13
As security for Lessee's total obligations in accordance with this agreement,
including payment of rent, water and heating expenses, obligations in connection
with moving etc. the Lessee shall pay upon signing this agreement DKK 752,556.25
corresponding to 3 months' rent. VAT shall be added to this amount.

The deposit shall be adjusted each year on 1 January so that it is always
equivalent to 3 months rent.

Sublease and Termination of Lease
(S)14
Subject to the Lessor's prior written consent the Lessee shall be entitled to
sublet the whole or part of the lease on unchanged lease conditions.

On the same condition as stated above the Lessee shall furthermore be entitled
to waive its rights and obligations as set forth in this agreement.

It is a condition for the Lessor's consent to sublease or waiver that the use of
the leased property is still in accordance with the objects as set forth in the
rules of the Science Park.

Termination of Lease
(S)15
The Lessor cannot terminate this Lease Agreement for 10 years. The Lessee cannot
terminate this Lease Agreement for 5 years.

The term of notice is 6 months to the first day of a month.  Thus, the notice to
terminate this Lease Agreement can be given at the earliest by the Lessor on 30
April 2010 for moving by 31 October 2010 and at the earliest by the Lessee on 30
April 2005 for moving by 31 October 2005.

Termination
(S)16
With respect to the Lessor's right to terminate this Lease Agreement reference
is made to Section 93 of the Danish Rent Act, however, it is emphasized that
termination as a consequence of late payment or other payment due as per this
contract can only take place if the Lessee has not effected payment not later
than 14 days after a written claim to that effect has been made to the Lessee.

The rent or other payment due that is not paid on the due date is, from that
date subject to a default interest of 1 per cent per month.
<PAGE>

                                       8

Moving
(S)17
In connection with moving, the leased property shall be returned in the same
condition as that in which it was taken over apart from deterioration due to
wear and ageing and that is not comprised by Lessee's duty to maintain the
leased property. In connection with moving an inspection shall be conducted by
representatives of the Lessor as well as the Lessee. Based on the moving
inspection a report shall be made on the state and condition of the lease at the
time of moving. The reports made in connection with moving in and moving out
together form the basis for any claims that may be made by the Lessor.

However, the Lessee is not under an obligation to return the leased property in
a state and condition better than it was at the time of taking over the leased
property.

The Lessee shall be obliged to re-establish any constructional changes if the
Lessor so wishes. This applies no matter whether or not the Lessor consented to
such changes.

The Lessee shall reimburse the Lessor for all expenses incurred in connection
with cleaning and clearing of the leased property as well as any renovation and
reestablishment so that the leased property appears in good condition, and
Lessee shall pay rent during the period of time where the renovation and
reestablishment takes place.

In connection with other Lessees' wishes to expand lease additional property in
the Science Park, the Science Park asks Lessees that to the extent necessary
they shall, after negotiation, accept moving to other leased property of the
same size and standard and at the same rent. The Science Park shall contribute
to the payment of necessary and reasonable moving and renovation costs, but will
not cover any loss on operations as a consequence of moving.

Insurance
(S)18
The Lessor shall take out a comprehensive building insurance.

If the Lessee's use of the rented space requires any specific insurance or an
increased premium the Lessee shall pay such expenses.

The Lessor shall not be obliged to insure any movable property belonging to the
Lessee.

Registration in the Danish Land Register
(S)19
The Lessee shall pay all expenses relative to the registration of this contract.

Furthermore, each party shall pay his own costs associated with entering into
this agreement.
<PAGE>

                                       9

The Danish Rent Act
(S)20
The rules of the Danish Rent Act shall apply to this lease provided that they
have not been departed from in any of the preceding sections. It is emphasized
that the Lessee is aware that the rules in this contract depart from the rules
of the legislation, and thus, the agreement confers more extensive obligations
on the Lessee and less extensive rights on the part of the Lessee as opposed to
the Lessor than provided for in legislation.

The general lease conditions applicable at any time for the independent
institution the Science Park in Horsholm shall also apply to this lease.

Special Conditions
(S)21
The Lessee has an option of renting an additional space of 335 m2 (inclusive of
shares space) on the ground floor and 467 m2 (inclusive of shared space) on the
first floor.

If the Lessee wishes to take advantage of this option the Lessor shall be
notified not less than 6 months prior to the date on which the Lessee wants to
take possession of the space. The space shall be reserved for the Lessee for not
more than one year so that the Lessor shall be notified of any exercise of the
option not later than 31 October 2000.

The final rent for the space shall be negotiated in connection with the possible
exercise of the option and the decoration and renovation of the space.

                            ----------oOo----------

Horsholm, 5 May 2000                 Horsholm, 1 May 2000

/s/ Preben Pamsgaard                 /s/ Jan Mikkelsen
/s/ Niels Moller                     /s/ Christian Hansen

The Science Park in Horsholm        ProFound Pharma A/S<PAGE>
                                                                     EXHIBIT 4.2

                         REGISTRATION RIGHTS AGREEMENT
                         -----------------------------

     This Registration Rights Agreement (the "Agreement") is entered into as of
                                              ---------
August  __, 2000 by and between HealthCentral.com, a Delaware corporation (the
"Company"), and AltaVista Company  (the "Stockholder").
--------                                 -----------

                                   RECITALS
                                   --------

     1.  The Stockholder has entered into an agreement with the Company dated as
of the date hereof (the "Stock Purchase Agreement") pursuant to which the
                         ------------------------
Company has agreed to sell to the Stockholder Three Hundred Thousand (300,000)
shares of the Company's Common Stock (the "Shares").
                                           ------

     2.  A condition to the Stockholder's obligations under the Stock Purchase
Agreement is that the Company grant certain piggyback registration rights to the
Stockholder with respect to the Shares.

     3.  The Company wishes to execute this Agreement and grant the Stockholder
the rights contained herein.

                                   AGREEMENT
                                   ---------

     The parties hereby agree as follows:

     1.  Registration Rights.  The Company and the Investors covenant and
         -------------------
agree as follows:

         1.1  Definitions.  For purposes of this Section 1:
              -----------

              (a) The terms "register," "registered," and "registration" refer
                             --------    ----------        ------------
to a registration effected by preparing and filing a registration statement or
similar document in compliance with the Securities Act of 1933, as amended (the
"Securities Act"), and the declaration or ordering of effectiveness of such
 --------------
registration statement or document;

              (b) The term "Registrable Securities" means:
                            ----------------------

                  (i)  the Shares; and

                  (ii) any other shares of Common Stock of the Company issued
as (or issuable upon the conversion or exercise of any warrant, right or other
security which is issued as) a dividend or other distribution with respect to,
or in connection with a stock split, or in exchange for or in replacement of,
the Shares, excluding in all cases, however, any Registrable Securities sold by
a person in a transaction in which his or her rights under this Agreement are
not assigned; provided, however, that Common Stock or other securities shall
              --------  -------
only be treated as Registrable Securities if and so long as they have not been
(A) sold to or through a broker or dealer or underwriter in a public
distribution or a public securities transaction, or (B) sold in a transaction
exempt from the registration and prospectus delivery requirements of the
Securities
<PAGE>

Act under Sectizon 4(1) thereof so that all transfer restrictions, and
restrictive legends with respect thereto, if any, are removed upon the
consummation of such sale;

              (c)  The term "Holder" means any holder of outstanding
                             ------
Registrable Securities who, subject to the limitations set forth in Section 1.10
below, acquired such Registrable Securities in a transaction or series of
transactions not involving any registered public offering;

              (d) The term "Form S-3" means such form under the Securities Act
                            --------
as in effect on the date hereof or any successor form under the Securities Act;
and

              (e) The term "SEC" means the Securities and Exchange Commission.
                            ---

         1.2  Company Registration.  If (but without any obligation to do so)
              --------------------
the Company proposes to register (including for this purpose a registration
effected by the Company for and upon the request of stockholders other than the
Holder(s) (a "Demand Registration")) any of its stock under the Securities Act
              -------------------
in connection with the public offering of such securities solely for cash (other
than a registration relating solely to the sale of securities to participants in
a Company stock plan or a transaction covered by Rule 145 under the Securities
Act, a registration in which the only stock being registered is Common Stock
issuable upon conversion of debt securities which are also being registered, or
any registration on any form which does not include substantially the same
information as would be required to be included in a registration statement
covering the sale of the Registrable Securities), the Company shall, at such
time, promptly give each Holder written notice of such registration; provided
                                                                     --------
however, that such notice shall not be required to be given and the Registrable
-------
Securities shall not be included in a Demand Registration if any shares that the
Requesting Holders (as defined in Section 1.3 hereof) have the right and desire
to include in such Demand Registration (as evidenced by the Requesting Holder(s)
written request) are excluded from such registration for any reason.  Upon the
written request of each Holder given within five (5) days after mailing of such
notice by the Company in accordance with Section 2.6, or in the case of the
registration statement currently proposed to be filed by the Company (notice of
which is hereby deemed to be given), upon written request given within two days
following the execution of this Agreement, the Company shall, subject to the
provisions of this Section 1.2 and Section 1.8 of this Agreement, cause to be
registered under the Securities Act all of the Registrable Securities that each
such Holder has requested to be registered; provided, however, that the time
                                            --------  -------
periods, filing procedures and manner of sale requirements governing such
registration, unless specifically addressed herein, shall be determined by the
Company's agreement with the Requesting Holders, or unilaterally by the Company
if there are no Requesting Holders, and provided further, that the Company shall
                                        -------- -------
not be obligated to cause any such registration, qualification or compliance,
pursuant to this Section 1.2 to become effective if the Company shall furnish to
the Holder(s) a certificate signed by the president of the Company stating that
in the good faith judgment of the Board of Directors of the Company, it would be
seriously detrimental to the Company and its stockholders for such registration
to be effected at such time, in which event the Company shall have the right to
defer the filing of the registration statement.

                                      -2-
<PAGE>

         1.3  Obligations of the Company.  Whenever required under this Section
              --------------------------
1 to effect the registration of any Registrable Securities, the Company shall,
as expeditiously as reasonably possible:

              (a) Prepare and file with the SEC a registration statement with
respect to such Registrable Securities and use its best efforts to cause such
registration statement to become effective, and keep such registration statement
effective (i) in the case of a Demand Registration on forms other than Form S-3,
for such period of time that the Company agrees with the stockholders requesting
the Demand Registration (such stockholders referred to herein as the "Requesting
                                                                      ----------
Holder(s)", which definition shall also include other Company stockholders
---------
holding shares with the identical registration rights as the Requesting
Holders), or (ii) in the case of other registrations effected by the Company or
Demand Registrations effected at the request of the Requesting Holder(s) on Form
S-3, for up to one hundred twenty (120) days or a shorter period during which
the Company and Holder(s) complete the distribution described in the
registration statement relating thereto, whichever first occurs.  The time
periods set forth in this section 1.3(a) shall take into account any period of
time during which the Holder(s) are prevented from utilizing the prospectus
because the Company notifies such Holder(s) that Prospectus Update (as defined
in Section 1.3(f) below) must be effectuated.

              (b) Prepare and file with the SEC such amendments and supplements
to such registration statement and the prospectus used in connection with such
registration statement as may be necessary to comply with the provisions of the
Securities Act with respect to the disposition of all securities covered by such
registration statement pursuant to the terms and subject to the conditions of
this Agreement.

              (c) Furnish to the Holder(s) such numbers of copies of a
prospectus, including a preliminary prospectus, in conformity with the
requirements of the Securities Act, and such other documents as they may
reasonably request in order to facilitate the disposition of Registrable
Securities owned by them.

              (d) Use its best efforts to register and qualify the securities
covered by such registration statement under such other securities or Blue Sky
laws of such jurisdictions as shall be reasonably requested by the Holder(s),
provided that the Company shall not be required in connection therewith or as a
--------
condition thereto to qualify to do business or to file a general consent to
service of process in any such states or jurisdictions.

              (e) In the event of any underwritten public offering, enter into
and perform its obligations under an underwriting agreement, in usual and
customary form, with the managing underwriter of such offering. Each Holder
participating in such underwriting shall also enter into and perform its
obligations under such an agreement.

              (f)  Notify each Holder of Registrable Securities covered by such
registration statement at any time when a prospectus relating thereto is
required to be delivered under the Securities Act of the happening of any event
as a result of which the prospectus included in such registration statement, as
then in effect, includes an untrue statement of a material fact or omits to
state a material fact required to be stated therein or necessary to make

                                      -3-
<PAGE>

the statements therein not misleading in the light of the circumstances then
existing, such obligation to continue for so long as the Company agrees to keep
the registration statement effective pursuant to the terms of Section 1.3(a),
whereupon each Holder shall cease utilizing such prospectus until such time as
the Company files a supplement or file a post-effective amendment to the
registration statement or the prospectus or any document incorporated therein by
reference or files any other report or document so that, as thereafter delivered
to the purchasers of the Registrable Securities, the prospectus will not contain
an untrue statement of a material fact or omit to state any material fact
necessary to make the statements therein not misleading (a "Prospectus Update").
                                                            -----------------
As soon as the Prospectus Update has been effectuated, the Company will notify
each Holder that the prospectus is available for use, whereupon each such Holder
may thereupon commence utilizing such prospectus.

              (g) Cause all such Registrable Securities registered pursuant
hereunder to be listed on each securities exchange on which similar securities
issued by the Company are then listed.

              (h) Provide a transfer agent and registrar for all Registrable
Securities registered pursuant hereunder and a CUSIP number for all such
Registrable Securities, in each case not later than the effective date of such
registration.

              (i) Use its best efforts to furnish, at the request of any Holder
registering their Registrable Securities pursuant to this Section 1, on the date
that such Registrable Securities are delivered to the underwriters for sale in
connection with a registration pursuant to this Section 1, if such securities
are being sold through underwriters, or, if such securities are not being sold
through underwriters, on the date that the registration statement with respect
to such securities becomes effective, (i) an opinion, dated such date, of the
counsel representing the Company for the purposes of such registration, in form
and substance as is customarily given to underwriters in an underwritten public
offering, addressed to the underwriters, if any, and to the Holder(s)
registering their Registrable Securities and (ii) a letter dated such date, from
the independent certified public accountants of the Company, in form and
substance as is customarily given by independent certified public accountants to
underwriters in an underwritten public offering, addressed to the underwriters,
if any, and to the Holder(s) registering their Registrable Securities.

         1.4  Furnish Information.  It shall be a condition precedent to the
              -------------------
obligations of the Company to take any action pursuant to this Section 1 with
respect to the Registrable Securities of any selling Holder that such Holder
shall furnish to the Company such information regarding itself, the Registrable
Securities held by it, and the intended method of disposition of such securities
as shall be required to effect the registration of such Holder's Registrable
Securities.

         1.5  Expenses of Registration.  All expenses incurred in connection
              ------------------------
with registrations, filings or qualifications of Registrable Securities pursuant
to Section 1.2 for each Holder (which right may be assigned as provided in
Section 1.10), including (without limitation) all registration, filing, and
qualification fees, printers' and accounting fees, and fees and disbursements of
counsel for the Company, shall be borne by the Company. The Company shall

                                      -4-
<PAGE>

not be required to pay any underwriters' or brokers' fees, discounts or
commissions relating to the Registrable Securities, or the fees or expenses of
separate counsel to the selling Holder(s).

         1.6  Underwriting Requirements.  In connection with any offering
              -------------------------
involving an underwriting of shares of the Company's capital stock, the Company
shall not be required under Section 1.2 to include any of the Holders'
securities in such underwriting unless they accept the terms of the underwriting
as agreed upon between the Company and the underwriters selected by it (or by
other persons entitled to select the underwriters), and then only in such
quantity as the underwriters determine in their sole discretion will not
jeopardize the success of the offering by the Company. If the total amount of
securities, including Registrable Securities, requested by stockholders to be
included in such offering exceeds the amount of securities sold other than by
the Company that the underwriters determine in their sole discretion is
compatible with the success of the offering, then the Company shall be required
to include in the offering only that number of such securities, including
Registrable Securities, which the underwriters determine in their sole
discretion will not jeopardize the success of the offering (the securities so
included to be apportioned pro rata among the selling stockholders according to
the total amount of securities entitled to be included therein owned by each
selling stockholder or in such other proportions as shall mutually be agreed to
by such selling stockholders), but in no event shall any Registrable Securities
be included if any shares held by the Requesting Holders are excluded. For
purposes of the preceding parenthetical concerning apportionment, for any
selling stockholder that is a Holder of Registrable Securities and that is a
partnership or corporation, the partners, retired partners and stockholders of
such Holder, or the estates and family members of any such partners and retired
partners and any trusts for the benefit of any of the foregoing persons shall be
deemed to be a single "selling stockholder," and any pro-rata reduction with
                       -------------------
respect to such "selling stockholder" shall be based upon the aggregate amount
of shares carrying registration rights owned by all entities and individuals
included in such "selling stockholder," as defined in this sentence.

         1.7  Delay of Registration.  No Holder shall have any right to obtain
              ---------------------
or seek an injunction restraining or otherwise delaying any such registration as
the result of any controversy that might arise with respect to the
interpretation or implementation of this Section 1.

         1.8  Indemnification.  In the event any Registrable Securities are
              ---------------
included in a registration statement under this Section 1:

              (a) To the extent permitted by law, the Company will indemnify and
hold harmless each Holder, any underwriter (as defined in the Securities Act)
for such Holder and each person, if any, who controls such Holder or underwriter
within the meaning of the Securities Act or the Securities Exchange Act of 1934,
as amended (the "Exchange Act"), against any losses, claims, damages, or
                 ------------
liabilities (joint or several) to which they may become subject under the
Securities Act, the Exchange Act or other federal or state law, insofar as such
losses, claims, damages, or liabilities (or actions in respect thereof) arise
out of or are based upon any of the following statements, omissions or
violations (collectively a "Violation"):  (i) any untrue statement or alleged
                            ---------
untrue statement of a material fact contained in such registration statement,
including any preliminary prospectus or final prospectus contained therein or
any amendments or

                                      -5-
<PAGE>

supplements thereto, (ii) the omission or alleged omission to state therein a
material fact required to be stated therein, or necessary to make the statements
therein not misleading, or (iii) any violation or alleged violation by the
Company of the Securities Act, the Exchange Act, any state securities law or any
rule or regulation promulgated under the Securities Act, the Exchange Act or any
state securities law; and the Company will pay to each such Holder, underwriter
or controlling person, as incurred, any legal or other expenses reasonably
incurred by them in connection with investigating or defending any such loss,
claim, damage, liability, or action; provided, however, that the indemnity
                                     --------  -------
agreement contained in this subsection 1.8(a) shall not apply to amounts paid in
settlement of any such loss, claim, damage, liability, or action if such
settlement is effected without the consent of the Company (which consent shall
not be unreasonably withheld), nor shall the Company be liable to any Holder,
underwriter or controlling person for any such loss, claim, damage, liability,
or action to the extent that it arises out of or is based upon a Violation which
occurs in reliance upon and in conformity with written information furnished
expressly for use in connection with such registration by any such Holder,
underwriter or controlling person.

              (b) To the extent permitted by law, each selling Holder will
indemnify and hold harmless the Company, each of its directors, each of its
officers who has signed the registration statement, each person, if any, who
controls the Company within the meaning of the Securities Act, any underwriter,
any other Holder selling securities in such registration statement and any
controlling person of any such underwriter or other Holder, against any losses,
claims, damages, or liabilities (joint or several) to which any of the foregoing
persons may become subject, under the Securities Act, the Exchange Act or other
federal or state law, insofar as such losses, claims, damages, or liabilities
(or actions in respect thereto) arise out of or are based upon any Violation, in
each case to the extent (and only to the extent) that such Violation occurs in
reliance upon and in conformity with written information furnished by such
Holder expressly for use in connection with such registration; and each such
Holder will pay, as incurred, any legal or other expenses reasonably incurred by
any person intended to be indemnified pursuant to this subsection 1.8(b), in
connection with investigating or defending any such loss, claim, damage,
liability, or action; provided, however, that the indemnity agreement contained
                      --------  -------
in this subsection 1.8(b) shall not apply to amounts paid in settlement of any
such loss, claim, damage, liability or action if such settlement is effected
without the consent of the Holder, which consent shall not be unreasonably
withheld; provided, that in no event shall any indemnity under this subsection
          --------
1.8(b) exceed the net proceeds from the offering received by such Holder, except
in the case of willful fraud by such Holder.

              (c) Promptly after receipt by an indemnified party under this
Section 1.8 of notice of the commencement of any action (including any
governmental action), such indemnified party will, if a claim in respect thereof
is to be made against any indemnifying party under this Section 1.8, deliver to
the indemnifying party a written notice of the commencement thereof and the
indemnifying party shall have the right to participate in, and, to the extent
the indemnifying party so desires, jointly with any other indemnifying party
similarly noticed, to assume the defense thereof with counsel mutually
satisfactory to the parties; provided, however, that an indemnified party
                             --------  -------
(together with all other indemnified parties which may be represented without
conflict by one counsel) shall have the right to retain one separate counsel,
with the reasonable fees and expenses to be paid by the indemnifying party, if
representation of

                                      -6-
<PAGE>

such indemnified party by the counsel retained by the indemnifying party would
be inappropriate due to actual or potential differing interests between such
indemnified party and any other party represented by such counsel in such
proceeding. The failure to deliver written notice to the indemnifying party
within a reasonable time of the commencement of any such action, if prejudicial
to its ability to defend such action, shall relieve such indemnifying party of
any liability to the indemnified party under this Section 1.8, but the omission
so to deliver written notice to the indemnifying party will not relieve it of
any liability that it may have to any indemnified party otherwise than under
this Section 1.8.

              (d) If the indemnification provided for in this Section 1.8 is
held by a court of competent jurisdiction to be unavailable to an indemnified
party with respect to any loss, liability, claim, damage or expense referred to
therein, then the indemnifying party, in lieu of indemnifying such indemnified
party hereunder, shall contribute to the amount paid or payable by such
indemnified party as a result of such loss, liability, claim, damage, or expense
in such proportion as is appropriate to reflect the relative fault of the
indemnifying party on the one hand and of the indemnified party on the other in
connection with the statements or omissions that resulted in such loss,
liability, claim, damage or expense as well as any other relevant equitable
considerations; provided, that in no event shall any contribution by a Holder
                --------
under this Subsection 1.8(d) exceed the net proceeds from the offering received
by such Holder, except in the case of willful fraud by such Holder. The relative
fault of the indemnifying party and of the indemnified party shall be determined
by reference to, among other things, whether the untrue or alleged untrue
statement of a material fact or the omission to state a material fact relates to
information supplied by the indemnifying party or by the indemnified party and
the parties' relative intent, knowledge, access to information, and opportunity
to correct or prevent such statement or omission.

              (e) Notwithstanding the foregoing, to the extent that the
provisions on indemnification and contribution contained in the underwriting
agreement entered into in connection with the underwritten public offering are
in conflict with the foregoing provisions, the provisions in the underwriting
agreement shall control.

              (f) The obligations of the Company and Holder(s) under this
Section 1.8 shall survive the completion of any offering of Registrable
Securities in a registration statement under this Section 1, and otherwise.

         1.9  Reports Under Securities Exchange Act of 1934.  With a view to
              ---------------------------------------------
making available to the Holder(s) the benefits of Rule 144 promulgated under the
Securities Act and any other rule or regulation of the SEC that may at any time
permit a Holder to sell securities of the Company to the public without
registration or pursuant to a registration on Form S-3, the Company agrees to:

              (a) make and keep public information available, as those terms are
understood and defined in SEC Rule 144, at all times so long as the Company
remains subject to the periodic reporting requirements under Sections 13 or
15(d) of the Exchange Act;

                                      -7-
<PAGE>

               (b) file with the SEC in a timely manner all reports and other
documents required of the Company under the Securities Act and the Exchange Act;
and

               (c) furnish to any Holder, so long as the Holder owns any
Registrable Securities, forthwith upon request (i) a written statement by the
Company that it has complied with the reporting requirements of SEC Rule 144,
the Securities Act and the Exchange Act, (ii) a copy of the most recent annual
or quarterly report of the Company and such other reports and documents so filed
by the Company, and (iii) such other information as may be reasonably requested
in availing any Holder of any rule or regulation of the SEC which permits the
selling of any such securities without registration.

         1.10  Assignment of Registration Rights. The rights to cause the
               ---------------------------------
Company to register Registrable Securities pursuant to this Section 1 may be
assigned by any Holder to a transferee or assignee of at least 50% of such
Holder's Registrable Securities, provided the Company is, within a reasonable
time after such transfer, furnished with written notice of the name and address
of such transferee or assignee and the securities with respect to which such
registration rights are being assigned; and provided, further, that such
assignment shall be effective only if immediately following such transfer the
further disposition of such securities by the transferee or assignee is
restricted under the Securities Act.

         1.11  Certain Additional Agreements of the Holder(s).
               ----------------------------------------------

               (a) Prior to and so long as the registration statement shall
remain effective, each Holder shall:

                   (i)   Not engage in any stabilization activity in connection
with the Company's Common Stock;

                   (ii)  Not bid for or purchase any of the Company's Common
Stock or any rights to acquire the Company's Common Stock, or attempt to induce
any person to purchase any of the Company's Common Stock other than as permitted
under the Exchange Act; or

                   (iii) Effect all sales of Registrable Securities in broker's
transactions through broker-dealers acting as agents, in transactions directly
with market makers or in privately negotiated transaction where no broker or
other third party (other than the purchaser) is involved.

               (b) Without limiting any other provision of this Agreement, no
Holder shall engage in any short-sales of the Company's Common Stock prior to
the effectiveness of the registration statement pursuant to which the Holder(s)
is offered the opportunity to sell its Registrable Securities hereunder, except
to the extent that any such short-sale is fully covered by freely tradable
shares of the Company's Common Stock.

         1.12  Termination of Registration Rights. The rights granted under this
               ----------------------------------
Section 1, including the rights to utilize any previously filed registration
statements, shall

                                      -8-
<PAGE>

terminate upon the earlier of (a) eighteen months following the date of this
Agreement, or (b) at such time as the Holder(s) may sell all of its Registrable
Securities in any single three month period pursuant to Rule 144 (or such
successor rule as may be adopted).

     2.  Miscellaneous.
         -------------

         2.1   Amendments and Waivers.  Any term of this Agreement may be
               ----------------------
amended or waived with the written consent of the Company and the holders of a
majority of the Shares then held by all Holders.  Any amendment or waiver
effected in accordance with this Section 2.1 shall be binding upon the parties
and their respective successors and assigns.

         2.2   Successors and Assigns.  Subject to the provisions of Section
               ----------------------
1.8, the terms and conditions of this Agreement shall inure to the benefit of
and be binding upon the respective successors and assigns of the parties.
Nothing in this Agreement, express or implied, is intended to confer upon any
party other than the parties hereto or their respective successors and assigns,
any rights, remedies, obligations, or liabilities under or by reason of this
Agreement, except as expressly provided in this Agreement.

         2.3   Governing Law. The corporate laws of the State of Delaware shall
               -------------
govern all issues concerning the relative rights of Company and the Stockholder
as a stockholder. All other questions concerning the construction, validity,
enforcement and interpretation of this Agreement and all acts and transactions
pursuant hereto shall be governed by and construed in accordance with the laws
of the State of California, without regard to principles of conflicts of law.

         2.4   Counterparts.  This Agreement may be executed in two or more
               ------------
counterparts, each of which shall be deemed an original and all of which
together shall constitute one instrument.

         2.5   Titles and Subtitles.  The titles and subtitles used in this
               --------------------
Agreement are used for convenience only and are not to be considered in
construing or interpreting this Agreement.

         2.6   Notices. Any notice required or permitted by this Agreement shall
               -------
be in writing and shall be deemed sufficient upon receipt, when delivered
personally or by courier, overnight delivery service or confirmed facsimile, or
48 hours after being deposited in the regular mail as certified or registered
mail (airmail if sent internationally) with postage prepaid, if such notice is
addressed to the party to be notified at such party's address or facsimile
number as set forth below (or as subsequently modified by written notice):

                                      -9-
<PAGE>

          To the Company:  HealthCentral.com
                           6001 Shellmound Street
                           Suite 800
                           Emeryville, CA  94608
                           Attention: Chief Financial Officer
                           Phone: 510-250-2600
                           Fax: 510-250-2701

                    With a copy at the same address to the attention of the
                    General Counsel, and a copy to:

                           Venture Law Group
                           2775 Sand Hill Road
                           Menlo Park, CA 94025
                           Attn:  Mark A. Medearis
                           Tel: 650-854-4488
                           Fax: 650-233-8386

          To the Holders:  AltaVista Company
                           1070 Arastradero Road
                           Palo Alto, CA 94304
                           Attn: General Counsel
                           Phone: 650-320-7700
                           Fax: 650-320-6433

         2.7   Severability.  If one or more provisions of this Agreement are
               ------------
held to be unenforceable under applicable law, the parties agree to renegotiate
such provision in good faith, in order to maintain the economic position enjoyed
by each party as close as possible to that under the provision rendered
unenforceable.  In the event that the parties cannot reach a mutually agreeable
and enforceable replacement for such provision, then (i) such provision shall be
excluded from this Agreement, (ii) the balance of the Agreement shall be
interpreted as if such provision were so excluded and (iii) the balance of the
Agreement shall be enforceable in accordance with its terms.

         2.8   Entire Agreement.  This Agreement is the product of all of the
               ----------------
parties hereto, and constitutes the entire agreement between such parties
pertaining to the subject matter hereof, and merges all prior negotiations and
drafts of the parties with regard to the transactions contemplated herein.  Any
and all other written or oral agreements existing between the parties hereto
regarding such transactions are expressly canceled.

         2.9   Advice of Legal Counsel.  Each party acknowledges and represents
               -----------------------
that, in executing this Agreement, it has had the opportunity to seek advice as
to its legal rights from legal counsel and that the person signing on its behalf
has read and understood all of the terms and provisions of this Agreement.  This
Agreement shall not be construed against any party by reason of the drafting or
preparation thereof.

                                      -10-
<PAGE>

         2.10  Delays or Omissions.  No delay or omission to exercise any
               -------------------
right, power or remedy accruing to any party to this Agreement, upon any breach
or default of the other party, shall impair any such right, power or remedy of
such non-breaching party nor shall it be construed to be a waiver of any such
breach or default, or an acquiescence therein, or of or in any similar breach or
default thereafter occurring; nor shall any waiver of any single breach or
default be deemed a waiver of any other breach or default theretofore or
thereafter occurring.  Any waiver, permit, consent or approval of any kind or
character on the part of any party of any breach or default under this
Agreement, or any waiver on the part of any party of any provisions or
conditions of this Agreement, must be made in writing and shall be effective
only to the extent specifically set forth in such writing.  All remedies, either
under this Agreement, or by law or otherwise afforded to any Holder, shall be
cumulative and not alternative.

         2.11  Third Parties.  Nothing in this Agreement, express or implied,
               -------------
is intended to confer upon any party, other than the parties hereto, and their
respective successors and assigns, any rights, remedies, obligations or
liabilities under or by reason of this Agreement, except as expressly provided
herein.

         2.12  Priority of Rights.  The registration rights granted to the
               ------------------
Holder(s) under this Agreement are intended by the parties to rank on a
subordinate basis to the rights granted to other holders of the Company's
capital stock to demand registration of such stock, and on a pari passu basis to
the piggyback registration rights held by other Company stockholders.  The
parties agree to interpret the terms of this Agreement in a manner consistent
with the foregoing intention.

                           [Signature Page Follows]

                                      -11-
<PAGE>

     The parties have executed this Agreement as of the date first above
written.

COMPANY:

HEALTHCENTRAL.COM

By:
   ---------------------------
   Albert L. Greene, President

STOCKHOLDER:

ALTAVISTA COMPANY

By:
   ---------------------------
   Kenneth R. Barber
   Chief Financial Officer

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