unidentified problem
 

i have a P4 2.2Ghz compaq system with 1Gb RAM, Vista ultimate & XP home dual boot system. the system shuts down unexpectedly & restarts after a few moments only to shut down & restart repeatedly. if i switch on after sometime it runs for sometime and same thing recurs again. after i changed to a higher capacity SMPS, the PC ran well for a few days but again the problem has restarted. it occurs both with XP & vista. the cooling fans seem to be running well & i have tried running the PC with all other hardware like DVD drive, modem, etc disconnected but same problem persists.
please help.
ramkumar

try to update all drivers.

Sounds likely to be a harware error.
Download a Linux boot cd, try booting to it and see if you get the same issue. If yes I would start testing your hardware, memory, power supply, cpu etc.

In no, make sure you have the latest and correct drivers for your system and all OS updates. (and up to date anti-virus program)

Ubuntu Home Page | Ubuntu

thanx for your suggestions.but i have the latest updates for my antivirus, OS, and drivers.incidentally the problem has not recurred again after i reset my BIOS settings.waiting now with my fingers crossed if it will recur.thanx a million again,
ramkumar

Hopefully it was only a bios conflit, if so you are very lucky.

*Just a bit of information.
The cause is usually as squirrelnmoose has said, a memory issue with OS specific data being corrupted, leaving the OS unsure what to do, thus is resets.
Motherboards can do this as well, a short in the board can send the kill signal, which would restart the computer as well.
Heating can be an issue, but more so in laptops, as long as the heatsink is still running properly that is not often a problem in desktops, there would be other signs before now if the case was becoming too warm.