**Exhibit
31.2**
   
   **CERTIFICATIONS**
   I, S.
Gregory Clevenger, certify that:
  (1)
    I
      have reviewed this annual report of Form 10-K on Mpower Holding
      Corporation;(2)
    Based
      on my knowledge, this report does not contain any untrue statement of a
      material fact or omit to state a material fact necessary to make the
      statements made, in light of the circumstances under which such statements
      were made, not misleading with respect to the period covered by this
      report;(3)
    Based
      on my knowledge, the financial statements, and other financial information
      included in this report, fairly present in all material respects the
      financial condition, results of operations and cash flows of the
      registrant as of, and for, the periods presented in this
      report;(4)
    The
      registrant’s other certifying officer and I are responsible for
      establishing and maintaining disclosure controls and procedures (as
      defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) and internal
      control over financial reporting (as defined in Exchange Act Rules
      13a-15(f) and 15d-15(f)) for the registrant and have:(a)
    Designed
      such disclosure controls and procedures, or caused such disclosure
      controls and procedures to be designed under our supervision, to ensure
      that material information relating to the registrant, including its
      consolidated subsidiaries, is made known to us by others within those
      entities, particularly during the period in which this report is being
      prepared;(b)
    Designed
      such internal control over financial reporting, or caused such internal
      control over financial reporting to be designed under our supervision, to
      provide reasonable assurance regarding the reliability of financial
      reporting and the preparation of financial statements for external
      purposes in accordance with generally accepted accounting
      principles;(c)
    Evaluated
      the effectiveness of the registrant’s disclosure controls and procedures
      and presented in this report our conclusions about the effectiveness of
      the disclosure controls and procedures, as of the end of the period
      covered by this report based on such evaluation; and(d)
    Disclosed
      in this report any change in the registrant’s internal control over
      financial reporting that occurred during the registrant’s fourth fiscal
      quarter that has materially affected, or is reasonably likely to
      materially affect, the registrant’s internal control over financial
      reporting; and(5)
    The
      registrant’s other certifying officer and I have disclosed, based on our
      most recent evaluation of internal control over financial reporting, to
      the registrant’s auditors and the audit committee of the registrant’s
      board of directors:(a)
    All
      significant deficiencies and material weaknesses in the design or
      operation of internal control over financial reporting which are
      reasonably likely to adversely affect the registrant’s ability to record,
      process, summarize and report financial information;
and(b)
    Any
      fraud, whether or not material, that involves management or other
      employees who have a significant role in the registrant’s internal control
      over financial reporting.
  
  Date:
    March
      14,
      2005
    By:
    /s/
      S. Gregory ClevengerS.
      Gregory ClevengerPrincipal
      Financial Officer