[General Questions and Answers] RoelVB:
Ok, here's what I did.

First to Enable DUN, which was removed since the introduction of internet sharing. (On the Cruise)

Import this keys into your registry

[HKEY_CURRENT_USER\Software\Microsoft\ATCmdInt]

[HKEY_CURRENT_USER\Software\Microsoft\ATCIV25T]
"TAPILineName"="Cellular Line"

[HKEY_LOCAL_MACHINE\Software\Microsoft\BTHATCI]
"Port"=dword:5

[HKEY_CLASSES_ROOT\atciuiapp\DefaultIcon]
@="shellres.dll,-8334"

[HKEY_CLASSES_ROOT\atciuiapp\SelectIcon]
@="shellres.dll,-8335"

[HKEY_LOCAL_MACHINE\Software\Microsoft\ATCIUI]
"WarningDisplayed"=dword:0
"Connections"=hex(7):53,00,65,00,72,00,69,00,61,00,6c,00,7c,00,43,00,4f,00,4d,\
00,31,00,3a,00,7c,00,31,00,31,00,30,00,20,00,33,00,30,00,30,00,20,00,36,00,\
30,00,30,00,20,00,31,00,32,00,30,00,30,00,20,00,32,00,34,00,30,00,30,00,20,\
00,34,00,38,00,30,00,30,00,20,00,39,00,36,00,30,00,30,00,20,00,31,00,34,00,\
34,00,30,00,30,00,20,00,31,00,39,00,32,00,30,00,30,00,20,00,33,00,38,00,34,\
00,30,00,30,00,20,00,35,00,36,00,30,00,30,00,30,00,20,00,35,00,37,00,36,00,\
30,00,30,00,20,00,31,00,31,00,35,00,32,00,30,00,30,00,20,00,31,00,32,00,38,\
00,30,00,30,00,30,00,20,00,32,00,35,00,36,00,30,00,30,00,30,00,00,00,49,00,\
72,00,43,00,4f,00,4d,00,4d,00,7c,00,43,00,4f,00,4d,00,33,00,3a,00,7c,00,00,\
00,55,00,53,00,42,00,7c,00,43,00,4f,00,4d,00,38,00,3a,00,7c,00,00,00,00,00
"ImplementationDLLs"=""
"LastConnectionIndex"=dword:0
"LastBaudRateIndex"=dword:8

Kopie all the files from the attached zip file into the \windows directory

Softreset the device

When you turn on bluetooth, the Dialup service will be available

Now we can configure the other device to use this Dialup service.

Using the Microsoft bluetooth stack (did not test this).

Go to Start > Settings > Connections > Bluetooth

Select or add the device with DUN enabled

Check the Dialup service for this device and save the settings

Go to Start > Settings > Connections > Connections

Choose 'Add new modem connection'

Give your connection a name, and select the modem type 'Bluetooth' and choose Next

Select the paired bluetooth you want to use and choose next

Now enter the phone number to dial, dial *99# to use your mobile internet connection and choose next

Now you have to fill in your providers username and password for your mobile internet connection. In my case (Vodafone, The Netherlands) the username and password have to be: vodafone

And Finish the wizard.

Using the WIDCOMM bluetooth stack.

Open the bluetooth manager

Create a new shortcut

Choose 'Connect to Internet via phone' and choose Next

Select your phone model (if listed) and choose Next

Make shure your phone's bluetooth is enable and set discoverable and choose Next

Select your phone, you will automaticly go to the next page

Insert a passkey you want to use to comunicate with your phone and choose Next

Accept the connection on your phone

Check the option 'Use this phone as default connection to the internet', Select 'new connection' and choose Next

Fill in a connection name and the phone number *99# (to use your phone's internet connection). And choose Next

Choose Finish to exit the wizard.

Go to Start > Settings > Connections > Connections

Choose 'Manage existing connections'

Choose Edit

Press Next a few times, until you get the username and password fields

Now you have to fill in your providers username and password for your mobile internet connection. In my case (Vodafone, The Netherlands) the username and password have to be: vodafone

And Finish the wizard.