Uncontrollable and sudden lag spikes in Windows 7, x64

Hello all, I've been having a little bit of a problem with my laptop lately, which is why I've come to ask for help here. (please excuse my iffy english)

My Dell XPS L401X laptop, has been running fine for the little over a year I've been using it.
However, since about a week ago, I've been experiencing some very random and extensive spikes in the CPU usage, followed by lag. I'll just be chugging along, working, gaming or doing who knows what, and it'll suddenly begin lagging and everything will go really slowly for a few seconds up to several minutes. The fan will become burning hot, and if I happen have audio playing at the time, it becomes very grainy, slow, and drawn out. This happens quite often and I can never tell exactly when it will occur.

I've scoured the Internet for people with similar problems (with no luck), and I've scanned my computer with MBAM, SUPERAntiSpyware, Comodo, Avira, all that fun stuff, so I'm pretty sure it isn't a virus. I've defragged it and run CCleaner. Nothing seems to work!
(At one point I did cleared my Chrome history, but my laptop ran noticeably faster for about 10 minutes). If I have Task Manager open, it says Skype, audiodg.exe, taskmgr.exe itself or something else is hogging all the CPU (20+).
The problem does not appear in Safe Mode.

I have no clue whatsoever what's causing this... any and all help is appreciated! Thank you in advance! (specs are in my profile)