Weird System Hang - Then Returns to Normal

Hi All

Wondering if anyone can shed a little light on this problem I am having. For a while now I have been having problems with my new setup, I upgraded to a 3.2Ghz Northwood and swapped the motherboard for an Asus P4C800-E Deluxe and all is fine, until you install SP2 (or I think its SP2 - I need to try it with SP1). The system runs fine when you boot up windows but after about 5 - 10 minutes the system will lockup and hang for 10 seconds with no activity at all then all of a sudden it will spring back to life, with the CPU at 100% load and the hard drive goes mental but all is fine.

For the last few weeks I have had this problem and I have tried all sorts, memory tests (which did show an error once out of 10 tests), making sure the heatsink is fine and seated correctly (temps are 26 - 29c idle and 43c @ load) the PSU rails are solid as the day I bought it, the hard drive is a few months old but tested in another machine and all is fine. So the only thing I have left that could be the problem is either Windows XP SP2 (read a few threads about issues with the prescott and later northwood chips - can't find the mentioned fix though.) or possibly the memory or soundcard.

I have a new sound card on the way today so that can be tested, I am testing a mates memory tonight to see if that memory error is the cause of the hang ups.

My system spec is:

Asus P4C800-E Deluxe
P4C 3.2Ghz Northwood 512kb L2 800Mhz
1gb Corsair 3200XL (2x512)
200GB Maxtor +9 Sata Hard Drive
XFX 6800GT 256MB
Hercules Game Theater XP 5.1
Enermax 550W PSU

I know its not a motherboard issue as my system had the same problems with the Abit IC7 Max3 I RMA'd for the same issue. When I got the new mobo it worked fine for the last week and now the problem has returned again. I have tested the cpu in another system with the same specs and it works fine, so I know its not the CPU, plus that has been RMA'd to and tested. It's an annoying problem and basically the system is unusable with it, there is no consistency to it, it will happen when ever and where ever it likes, I can be watching a video and it will hang then return to normal, browsing the web and it locks up and returns to normal after a few seconds, playing games, listening to music, anything really.

Has anyone had this problem or seen it before and know what it can be caused by? I have seen a few posts and been told there is a fix for Win XP for this but can I heck find it :/ if anyone can suggest anything I am willing to listen, I have tried everything under the sun and it still having issues :/

Any suggestion is welcome.

Cheers

Fox

EDIT: Forgot to add this happens on a fresh build and after updates have been added etc.

well i have ran perfmon in windows to see if i can log whats happening but when the system hangs it obviously stops recording leaving a huge gap in the monitor display so i cant tell whats going on, anyone got any idea's?

Slight edit, been told from someone who's had the same problem and they say it was their raptor HD, i aint using a raptor but is there any other way to test a HD without just checking for errors?