CPU usage issues

[Superschizo]

I'm currently running on a custom built PC. Running on XP. I've got;

LGA 775 Pentium 4 processor,
2 gigs DDR2 ram,
GeForge 8600GTS graphics card,
Some nVidia mobo (if it's necessary I can get the actual model),
about 300gigs harddrive space.

My problem is, my PCU usage is sitting at about.. 70%-100%. Less than 48 hours ago, this wasn't a problem, I was running all my games at 60fps+, no lag issues at all. And now, it's gotten to the point where opening new tabs in Firefox is causing my PC to freeze up.

I've tried a few things in hopes of fixing this; Anti-virus software, making sure everything is hooked in properly, closing processes that weren't necessary, etc.

Yet it's all gone without result.

Are there any known fixes for this?

 

[Superschizo]

Well, it seems my CPU usage only really hits those high numbers when I'm running a game of sorts. Which is a little odd, seeing as less than two days ago, I could run three games at the same time and hardly suffer at all.

 

[Ruthe]

Super. Have you got a firewall, virus and malware protection? That's all the ideas that occur at the moment.

Maybe reposting under a different forum will get better a response.

 

[Ruthe]

Also, I just noticed this. Has a few more suggestions.
https://www.techspot.com/vb/topic55152.html