As GTS noted:
1. What is running in the background:
Windows XP Startup Programs Tracker
http://www.kellys-korner-xp.com/xp_u.htm#xp_util
Belarc: For a detailed list of all installed software:
http://www.belarc.com/Download.html
In the Software Versions section you'll see all of your installed software.
At the end of each entry is a clickable asterisk that will take you to the
folder the software is installed in.
2. Is your system clean?
Run Ad-Aware SE, Spybot and HijackThis:
http://www.majorgeeks.com/downloads31.html
Note: Update the first two programs, once installed, before running.
Free Online Virus Scan
http://housecall.trendmicro.com/housecall/start_corp.asp
3. When did this behavior start? After doing ........
4. By default when WinXP encounters a system failure, it reboots without
warning. The setting that controls this can be changed:
Control Panel/System/Advanced/Settings (Startup & Recovery)/System
Failure/Uncheck-Automatically Restart.
You can use Event Viewer to view and manage the event logs, gather
information about hardware and software problems, and monitor Windows
security events.
To view the event log: Administrative Tools/Event Viewer or
Start/Run/eventvwr.
To review Shutdown Event Tracker data, Open Event Viewer. Click System Log,
scroll to the Event column, and find entries with the number 1075.
HOW TO: View and Manage Event Logs in Event Viewer in Windows XP
http://support.microsoft.com/default.aspx?scid=kb;EN-US;q308427
And also:
Go to Start/Run/Msinfo32/Hardware Resources, Components/Problem Devices and
Software Environment/Windows Error Reporting.
Go to Help and Support/Pick a Task (left side)/Use Tools to view.../(left
pane)My Computer Information/(right pane)View the status of my system
hardware and software/Hardware/Update and Troubleshooters.
How to Troubleshoot Hardware and Software Driver Problems
http://support.microsoft.com/default.aspx?scid=kb;en-us;Q322205
Try running the DirectX Tool: Start/Run/Dxdiag, Lower Hardware Acceleration
(Display/Settings/Advanced/Troubleshoot/Hardware Acceleration). Check
System Info for problematic issues: Start/Run/Msinfo32/Hardware Resources
and Components/Problem Devices and Software Environment/Windows Error
Reporting.
Good luck and keep us posted.
--
In memory of our dear friend, MVP Alex Nichol:
http://www.dts-l.org/
All the Best,
Kelly (MS-MVP)
Troubleshooting Windows XP
http://www.kellys-korner-xp.com