Suggestions: I have seen this related to CD and CDRW issues. One being
that a CD is in the drive during the restart process. Also check for
updates concerning your network, video, sound and bios.
Another checkpoint would be to boot into safe mode and check off Selective
Startup (Msconfig), uncheck all other boxes, reboot. If this helps,
troubleshoot from there.
Added info:
Windows Boots without warning!
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
--
All the Best,
Kelly (MS-MVP/DTS&XP)
Taskbar Repair Tool
http://www.kellys-korner-xp.com/taskbarplus!.htm