It is windows bug. Has someting to do with windows update and the svchost file. It only lasts until windows update is finished.
That's a Windows 2000 and Windows XP bug for people using Microsoft Update mainly which they patched months ago. There is a patch on the Microsoft website if the OP thinks that Windows Update is the problem. I've had to patch a few PCs which had their 2Ghz AMD Sempron Processors get choked for 5 minutes at a time.
Help me, I've taken out my heatsink and cleaned it (i have not removed its thermal paste) and installed it. But now my pc is not starting (it is getting off after 4 - 5 sec)
That can be for a number of reasons. Everyone here seems to be saying it's due to overheating. In that case, definitely check the heat sink to make sure it's secure and I hope you applied some decent paste properly (the way you'd apply Arctic Silver or IC Diamond or for that matter, any paste). Also if the processor came out with pulling the heat sink, I'd definitely check your pins as well to make sure nothing is bent or missing. There are processor pin diagrams on the Internet which show what each pin is made for. Each processor will typically have a few unused pins. So really, double check your work and make sure it's left clean and secure.
I've seen the bent pin thing happen a lot. A good example is someone who came to me asking me to see why their new motherboard wasn't POSTing (they replaced it themselves since the one I bought for them had the Northbridge cook on it). First thing I checked was the heat sink and CPU assembly and saw bent pins. They didn't even notice their CPU was glued to the heat sink (thermal paste they gave me to use turned into glue) when they took the heat sink out as well as put it in which was why those pins were bent. Using a mechanical pencil to bend the pins back and putting the processor in properly fixed it right up
. I had fixed that machine before (had to replace the motherboard, those Dell OptiPlex GX280s are terrible for fried capacitors/components on the motherboard) and I know I didn't bend any pins since the PC was able to boot just fine when I replaced the motherboard initially and I inserted it properly too.