Windows update error

Hi,

We face below mentioned issue in installing the patch .

Log Name:      System
Source:        Microsoft-Windows-WindowsUpdateClient
Date:          9/20/2012 8:55:00 PM
Event ID:      20
Task Category: Windows Update Agent
Level:         Error
Keywords:      Failure,Installation
User:          SYSTEM
Computer:     
Description:
Installation Failure: Windows failed to install the following update with error 0x80070643: Security Update for SQL Server 2005 Service Pack 4 (KB2494120).
Event Xml:
<Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">
  <System>
    <Provider Name="Microsoft-Windows-WindowsUpdateClient" Guid="{945A8954-C147-4ACD-923F-40C45405A658}" />
    <EventID>20</EventID>
    <Version>0</Version>
    <Level>2</Level>
    <Task>1</Task>
    <Opcode>13</Opcode>
    <Keywords>0x8000000000000028</Keywords>
    <TimeCreated SystemTime="2012-09-20T18:55:00.477062500Z" />
    <EventRecordID>39541</EventRecordID>
    <Correlation />
    <Execution ProcessID="828" ThreadID="5268" />
    <Channel>System</Channel>
    <Computer>
    <Security UserID="S-1-5-18" />
  </System>
  <EventData>
    <Data Name="errorCode">0x80070643</Data>
    <Data Name="updateTitle">Security Update for SQL Server 2005 Service Pack 4 (KB2494120)</Data>
    <Data Name="updateGuid">{4D342937-B753-4491-B57D-9304E4F084BC}</Data>
    <Data Name="updateRevisionNumber">101</Data>
  </EventData>
</Event>

Regards, Ajit