CPU is unworkable

[#1]

A Friend of mine has asked me about a problem with his fairly old (4years) computer.
On boot up the following message is displayed,  CPU is unworkable or has been changed please check CPU Soft Menu..... Press f1 to continue or delete for setup.
If he presses f1 the boot process starts again but continues and windows XP  fully loads and works OK.
He has tried windows repair but the problem remains.
OK I know he should get a new computer or just press f1 each time he boots up and forget about it so its more of a curiosity thing than anything else, has anyone else come across this problem, and could it be an indicator of problems to come ?
CPU is an Athlon 2200
I think the motherboard is a MSI  K7  ?
Any advice I can pass on to him would be appreciated
Thanks

[#2]

at four years old the thermal paste between the cpu and the heatsink could have broken down.  arctic silver paste is a good replacement and isopropyl alcohol will clean off the old stuff.  has he checked that all his fans are rotating and that there's no muck in the machine?

[#3]

Have you checked the CPU Soft Menu?
I guess this is a BIOS option...

[#4]

Axisofevil,
To be honest I am not sure what I should be looking at when in the CPU soft menu ?........ Plenty of figures there like 133 but most of the boxes are grayed out. There is an option to put user options in but I don't know enough to start fiddling around with this.
One thing I should have mentioned in the earlier post is that the computer was failing to keep the correct time so the battery was replaced, could this have any bearing on the problem & if so where do we go from here ?
 

[#5]

Sounds like that it has lost its BIOS settings when the CMOS battery  failed. When you enter the BIOS, there should be an option to revert to default values, that will work, and then press the key to save settings and exit BIOS (usually f10) I would do this, and also as artificer has suggested, I would put new thermal paste on the CPU, for good measure.

[#6]

If it was overheating it wouldn't boot when F1 pressed - it would just die (personal experience!!!)

[#7]

Thanks for your suggestions, problem now sorted,
Thanks

[#8]

Any clues as to the diagnosis/resolution in case it applies to anybody else in future?