Yay! For computer troubles!

So a couple of days ago my PC started playing up. It first started with with just the internet being abnormally slow, at the time I thought nothing of it, especially as my dad's PC was a bit slow surfing the internet as well. However this problem seems to have spread beyond my PC, random intervals my internet will dive for about 20 seconds, pages will just sit there doing nothing, supposedly loading but then without warning the page will load. That's not the end of the world I suppose but the main problem, the one really affecting my PC is when I open a program, any program, even spider solitaire causes the system to go into melt down, CPU usage will sky rocket to 100% but there's no apparent program or process using all that processing power, the odd program will spike to 50%+ but then go down again a few seconds later. This'll last for about 5-10 minutes, leaving me with nothing to do but twiddle my thumbs (or whip out my good ol' DS, I'd forgotten how good Polarium is!).

It seems to be a pretty common problem, a search on google turns out hundreds or results (as per usual) all detailing the same problem (minus the internet stuff, evidently a different problem all together). So you'd think I've have this issue sorted in no time, right? what with all those results on google. Well no, while loads of people seem to have the same problem (100% cpu usage for no apparent reason) there seems to be a 101 reasons as to why it happens, some people have fixed it by turning off windows automatic update, some have re-installed zone alarm, a few have had problems with the latest version of Winamp (version 5.52 for those of you who want to know), some have taken the drastic measure of wiping the hard drive and starting afresh. so far I've only the first of those, along with some other things like cleaning up my cache and registry, doing a very probing virus/spamware/malware scan, they turned a couple of things, none of which would cause the system to become unusable.


Despite all this though I think I know the true reason why my system is fucked at the moment, and it all comes down to one games company, EA. I downloaded the demo to battlefield 2142 and when I first ran the install exe things started to go tits up, coincidence? Maybe, I'm not so sure though. Either way I've uninstalled the demo but the damage seems to be done. I wasn't a big fan of EA before and if that demo does turn out to be the cause of my troubles then my opinion of them will plummet even further, as far as I'm concerned their only saving grace is Criterion, the makers of Burnout, while buying them out wasn't necessarily the best thing to do, they did have the smarts to just leave them to it.

Anyway 100% CPU usage, annoying. Any suggestions as to how to fix it are more then welcome.

This is Benji Dude, asking you to take a walk in my shoes.

Edit:
Well I seem to have fixed, seems the source of all this grief was Zone Alarm. Sorry about that EA... kinda...