Windows 7 PC crashes after being locked a few minutes

Question

I have a problem with an Optiplex 755 PC running (32-bit) Windows 7 Professional. I just installed the operating system last week, and ever since, it seems to crash when I lock the screen. It doesn't happen immediately; it's usually after I walk away, so a few minutes (but I'm not sure exactly how many).

I have this non-specific error in the Event log. I've run a chkdsk, thinking it might be hard drive-related, but that didn't help. Any ideas on what to check and how are appreciated.

Log Name:      System
Source:        Microsoft-Windows-Kernel-Power
Date:          11/17/2010 3:09:28 PM
Event ID:      41
Task Category: (63)
Level:         Critical
Keywords:      (2)
User:          SYSTEM
Computer:      WORKSTATION.domain.local
Description:
The system has rebooted without cleanly shutting down first. This error could be caused if the system stopped responding, crashed, or lost power unexpectedly.
Event Xml:
<Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">
  <System>
    <Provider Name="Microsoft-Windows-Kernel-Power" Guid="{331C3B3A-2005-44C2-AC5E-77220C37D6B4}" />
    <EventID>41</EventID>
    <Version>2</Version>
    <Level>1</Level>
    <Task>63</Task>
    <Opcode>0</Opcode>
    <Keywords>0x8000000000000002</Keywords>
    <TimeCreated SystemTime="2010-11-17T20:09:28.627614200Z" />
    <EventRecordID>6250</EventRecordID>
    <Correlation />
    <Execution ProcessID="4" ThreadID="8" />
    <Channel>System</Channel>
    <Computer>WORKSTATION.domain.local</Computer>
    <Security UserID="S-1-5-18" />
  </System>
  <EventData>
    <Data Name="BugcheckCode">0</Data>
    <Data Name="BugcheckParameter1">0x0</Data>
    <Data Name="BugcheckParameter2">0x0</Data>
    <Data Name="BugcheckParameter3">0x0</Data>
    <Data Name="BugcheckParameter4">0x0</Data>
    <Data Name="SleepInProgress">false</Data>
    <Data Name="PowerButtonTimestamp">0</Data>
  </EventData>
</Event>

Answer 1

If the screen shuts off while it is locked you are more than likely experiencing a video driver problem. A good test to perform would be to remove the driver and run with the windows native one, or alternatively you could press f8 at boot and load VGA mode. Test locking it and letting it sit for a few minutes I think you will find that it is no longer crashing. The next step would be to find new drivers or old ones that work, let me know if you need help with this.