One for the computer experts.

I would say either power supply, memory or overheating. 

It's unlikely you'd suddenly be drawing too much power for your power supply to handle, but it could be on its way out I suppose.

Most bizarre problems I've had I've traced to faulty or incompatible memory try running this to check your memory thoroughly
http://www.memtest.org/

Finally, keep an eye on your CPU and system temperatures, your motherboard probably comes with a utility to show you these, you might be overheating due to the warmer weather. 

With regards to removing the game you've done what I'd suggest, once all trace is gone from the registry it should be fine, my guess would be that there's still an entry somewhere.  I have a similar thing with a wireless driver, waiting for my next re-install to clear that.

Buy and install Norton Systemworks (includes antivirus). It will automatically keep your registry clean, remove internet clutter, check for viruses and loads of other things.

I was sceptical before I was given a copy as a gift. I now think it is good value and does a good job.

There is also the option to buy it bundled with Personal Firewall, which also works if you have not got one.

nero wrote: Looking back at previous posts, haven't you recently upgraded Video Card and possibly a Power Supply - where are you at with these upgrades?

I have upgraded the graphics card but ended up sticking with the original PSU. However it has been fine for about 2 months and according to everyone I've spoken to the PSU should be able to cope with the card. I suspect it was the heat, but i also think it could be something nasty that got onto my PC via the COD2 online game server since I have to allow it access through my fire wall.

If you suspect that it is heat, how about fitting an extra fan?

I fitted a PCI Slot Fan from Maplins - something like this one
It worked really well and it was amazing to see how much heat it pulls out of the case  

I have an Nvidea GE Force 7600gt, a dell 305W PSU, a dvd/cd R/W drive and a 120gb hard drive and that's about it. I know that a 350W PSU is recomended for the card but they also recommend the same for the 7800GT which is a lot more power hungry than mine. People in the know have told me it will be ok.

Anyway i've not had the problem since, although I haven't played any games for any length of time.

I've now contacted activision about the problem with COD2.

I did a restore from before I intalled the game and I was able to reinsstall it. However I uninstalled and reset the restore after I got a 'blue screen of death' informing me the PC was shutting down to prevent damage twice.