Have a problem with comp shutting randomly shutting down for no reason

When I reboot I get message " OVerclocking Failed" please press F1 to enter Bios, press f2 to reset bios to default".

I have never overclocked my PC so do not understand this, has happened 3 times in last 24 hours.

No new software has been installed and the only hard ware change was an upgrade pf my PSU to 500W about 2 months ago.

Have never seen this message before and am stumped, would really appreciate any help or advice.

My specs are:

Pentium 4 - 3.2 Ghz
Asus P4P800Deluxe mobo
1Gb dual channel Ram
500W Antec PSU
Nvidia FX5900XT Graphics
80Gb IBM Deskstar 7200
60Gb Maxtor Diamond 7200
Audigy 2 Soundcard
Toshiba 16x DVD Rom
Pioneer 110d 16x DVD Writer
Samsung Syncmaster 970P 19" TFT

Windows XP Professional +SP2

Thanks

Download CPU-Z If the clock speed are changing, throttling or BIOS thing. Check your VCore.

Also check your BIOS and assure that there is no overclock options set.

Think I have solved it, have monitored CPU temp which is currently running at 76C, I know P4's tend to run hot but this I think is too hot, I think the CPU fan has somehow come adrift from the processor thereby showing increased heat. Motherboard is running at 51C which again is little high.
To be on the safe side I am fitting new fan and heatsink which I hope will cure it.

Thanks for everbodies help and advice it is very much appreciated.

Sounds like another case fan might help as well.