If you face  below error in your application event log on your SharePoint 2010 installation, find which account is running mssearch.exe  and assign full permissions on HKLM\SYSTEM\CurrentControlSet\Services\VSS\Diag to the account.

  

Log Name:      Application

Source:        VSS

Date:          7/1/2010 11:40:19 PM

Event ID:      8193

Task Category: None

Level:         Error

Keywords:      Classic

User:          N/A

Computer:      Sp2010Dev.colors.test

Description:

Volume Shadow Copy Service error: Unexpected error calling routine RegOpenKeyExW(-2147483646,SYSTEM\CurrentControlSet\Services\VSS\Diag,...).  hr = 0x80070005, Access is denied.

.

 

Operation:

   Initializing Writer

 

Context:

   Writer Class Id: {0ff1ce14-0201-0000-0000-000000000000}

   Writer Name: OSearch14 VSS Writer

   Writer Instance ID: {311c68e7-e546-4f17-8aa4-277dd666b22e}

Event Xml:

<Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">

  <System>

    <Provider Name="VSS" />

    <EventID Qualifiers="0">8193</EventID>

    <Level>2</Level>

    <Task>0</Task>

    <Keywords>0x80000000000000</Keywords>

    <TimeCreated SystemTime="2010-07-01T20:40:19.000000000Z" />

    <EventRecordID>3160</EventRecordID>

    <Channel>Application</Channel>

    <Computer>Sp2010Dev.colors.test</Computer>

    <Security />

  </System>

  <EventData>

    <Data>RegOpenKeyExW(-2147483646,SYSTEM\CurrentControlSet\Services\VSS\Diag,...)</Data>

    <Data>0x80070005, Access is denied.

</Data>

    <Data>

 

Operation:

   Initializing Writer

 

Context:

   Writer Class Id: {0ff1ce14-0201-0000-0000-000000000000}

   Writer Name: OSearch14 VSS Writer

   Writer Instance ID: {311c68e7-e546-4f17-8aa4-277dd666b22e}</Data>

    </EventData>

</Event>