Sound lag

After upgrading my computer from vista 32bit to windows 7 64x I have noticed that, while listening to music in WMP or Winamp, I will get sound lag.
The music will sort of slow down a lot giving me this annoying sound, and then go back to normal speed.
This mostly happens when I use any internet browser (Firefox, IE, Opera and Chrome).
This is of course immensely irritating as I should have plenty of resources to browse the internet and listen to music.
Sometimes I will also be playing FM11 with music and browser running. While doing this CPU peaks at 12% usage and I have roughly 2 GB ram available.

I have (of course) checked for any viruses, or programs using excessive amounts of memory or CPU power. I Have also checked for spyware, and cleared cookies etc.
I am quite lost here, since I don't see any reason for this lag so any help would be appreciated.


Edit-
It would seem that the issue here is my CPU, but the temperature of it is fine.
Also, I am not just experiencing sound lag, but also overall lag.