My CPU usage isconstantly jumping up and down.?

[hissingnumber220]

I just got a new motherboard, and since then I've had nothing but problems with my cpu usage, its okay for 1-2 minutes but then it jumps up to 80-95 for no apparent reason.
My rig:
GeForce GTX 650 Ti
Intel® Core™ 2 duo CPU E8400 @ 3.00GHz
4.00 GB RAM (3.94 GB usable)
Microsoft Windows 7 Ultimate.
Not please don't pull the "your pc is slow", I think my PC should be able to run google chrome without going to 100 cpu usage. I used to be able to play most games on my pc without any problem, now i cant use skype.
Please help me out here, I'm dying
I've brought the PC to people to fix it, every friggin' ït specialist" just reinstalls the windows and says it works, well it doesn't, I don't call a 100% cpu usage with only skype and 1-2 programs in the background a working pc.
"Reinstall your windows"
-Its been reinstalled 3 times in close to a single week.
"Have you tried switching it on and off again"
-Yes...
"Use task manager and see what program is using the most % cpu usage"
-I only have 3 programs installed currently. Even with skype off (which is using the most cpu power) the pc goes to hell.
"Run it in safe mode"
- Tried it, same shit, different packaging.
My PC does not in any way run good with 100% cpu, it can bearly run a game from 10 years ago, while as previously said I used to be able to play pretty much anything without issues.