Getting random reboots without BSOD (Win7 x64)

I've been getting random reboots and I have no idea why this is happening. It just restarts without getting a BSOD or any other error message.

Today, it rebooted at 5:07 AM and at 12:47 PM. At both of these times, I wasn't using the computer, it was just sitting there.

At 5:07 AM notable open apps were: Chrome, VMWare Workstation (1 VM), Eclipse, Android emulator.

At 12:47 PM notable open apps were: Eclipse, Android emulator.

I've attached the diagnostic data but here are some relevant system events:

Code:

Log Name:      System
Source:        EventLog
Date:          8/15/2012 12:50:19 PM
Event ID:      6008
Task Category: None
Level:         Error
Keywords:      Classic
User:          N/A
Computer:      YuyuPC
Description:
The previous system shutdown at 12:47:50 PM on ‎8/‎15/‎2012 was unexpected.
Event Xml:
<Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">
  <System>
    <Provider Name="EventLog" />
    <EventID Qualifiers="32768">6008</EventID>
    <Level>2</Level>
    <Task>0</Task>
    <Keywords>0x80000000000000</Keywords>
    <TimeCreated SystemTime="2012-08-15T17:50:19.000000000Z" />
    <EventRecordID>350482</EventRecordID>
    <Channel>System</Channel>
    <Computer>YuyuPC</Computer>
    <Security />
  </System>
  <EventData>
    <Data>12:47:50 PM</Data>
    <Data>‎8/‎15/‎2012</Data>
    <Data>
    </Data>
    <Data>
    </Data>
    <Data>27461</Data>
    <Data>
    </Data>
    <Data>
    </Data>
    <Binary>DC07080003000F000C002F0032003B03DC07080003000F0011002F0032003B03600900003C000000010000006009000000000000B00400000100000000000000</Binary>
  </EventData>
</Event>

Code:

Log Name:      System
Source:        Microsoft-Windows-Kernel-Power
Date:          8/15/2012 12:50:03 PM
Event ID:      41
Task Category: (63)
Level:         Critical
Keywords:      (2)
User:          SYSTEM
Computer:      YuyuPC
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="2012-08-15T17:50:03.752414500Z" />
    <EventRecordID>350486</EventRecordID>
    <Correlation />
    <Execution ProcessID="4" ThreadID="8" />
    <Channel>System</Channel>
    <Computer>YuyuPC</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">129895264769180955</Data>
  </EventData>
</Event>

I would appreciate any help. Thanks!

It happened 2 more times yesterday. I'm running out of ideas. Can someone help?

Still happening frequently. Can anyone help? If I haven't provided all the necessary information you need, please let me know. Thanks!