System + System Interrupts

Hello everyone, sorry if this matter has been adressed before, but I used the search feature to narrow down what my problem is and avoiding to double post.

I have a desktop PC, ATI Radeon 4850 HD, 1T SATA HardDrive, Pentium DualCore 2.5 and an MSI MotherBoard sorry but I dont recall the name, but it's 4 years old.

Most of the time my CPU usage is always above 50%, was 80-85% with Win 7, with System + System Interrupts eating most of the CPU.

This never happened to me before, but it started since I had to format my PC and I instaled windows 7. Then I formated again...and again, now the last time with Win8 Pro 64 bit, to see if the issue would stop. However no avail, it does not eat so much CPU now, but still, its suficient to play games with a crappy framerate. I could play Tombrider, the last one, super smooth before, now...lolol Not League of Legends, which ran at 60+ FPS, escapes the System Interrupts of Doom.

I've spent hours looking for a solution, I've disabled the boost efects from my playback devices, ran registry scans...well...some options and with no sucess at all. I've updated the drivers from the gfx card and sorts aswell.

I'll provide a screenshot of the taskmanager and hope that I can get some input on this matter.

Thank you very much!

System interrupts (and the "System" process in general) are ways to represent the behavior of the Windows kernel and drivers that live therein. If you see a high "System" CPU percentage and a corresponding "System interrupts" percentage, you've got a driver causing that and it could be almost anything. There are ways to trace it, of course, using the Windows Performance Toolkit, but a quicker way to figure it out is to download all of the latest certified drivers for your hardware from the computer manufacturer or Windows update for Windows 8, then go offline and uninstall any antivirus, antimalware, firewall, or other computer monitoring/cleaning software and see if the problem persists. If so, *then* we put the A/V back on and get a trace via the WPT. That's the first and best suggestion I have before going after any data to figure it out.