Ask your friend if he's been doing some overclocking? Maybe he raised the voltage too far and it's shutting down because its hot? Or maybe he raised the FSB too high and not enough voltage and its restarting because its unstable?
Another possibility may be that the fan is clogged with dust or something and its shutting down because its overheating that way. I'm lead to believe this is the case because you said it was getting worse by the minute, which is understandable if you're turning it back on before it has time to cool down.
[CPU: e6600 @ 3300 MHz] // [MB: ASUS P5N-E SLi] // [RAM: Patriot 'eased latency' PC2-6400 @ DDR800 5-4-4-12-2T] // [GPU: 8800GTX @ 650/1000/1600 (volt modded)] // [HDD: 2x Cavier 500GiB stripe] // [Chassis: Thermaltake Armor VA8000 (black)] // [PSU: Aspire(Apevia) 680w] // [OS: Windows 7 Ultimate x64][Cooling: water cooled GPU and CPU]
^ (9/7/2010): Ha, I remember when that was the stuff. My water cooling has since leaked and fried my mobo. So now I'm rocking an MSI laptop with an i5 430m :)