High/weird cpu processor usage and around 20-25% system interrupts.

[[M.V.P] VolcanoHigh]

Hello

I use a AMD phemon IIx4 965 processor. (never had proplems with this till now.) One of its cores is reading usage ranging 70-99% in the task manager performance while the other 3 are working normally/reading normal numbers. The issue comes randomly but wont go away unless i restart my computer. This problem popped up a week a go, i was playing a game in steam when i noticed drastic performance drop and started to investigate. The issue something comes when im not gaming. I use my computer mainly on gaming. The computer slows down cause of this. I have no idea whats causing it. HELP?!

Procexp says system interrupts 20-25. Acording to CPU-Z and CrystaldistInfo my HDD temperatures are all normal, around 28-38C when idle.

Reasently i got a new case for my computer parts, i removed and switched my components from my old case to a new one. I tried to be careful and i know (i thinki know.) enough of computers to do this by my self. Done it a fey times in the past. I read the instructions and put/connected all the wires and parts according to them. The machine booted up normally. No issues. Could this have caused this issue, is a wire in the wrong place? I dont know.

I used free versions of Windows security essentials, Spybot search and destroy, Avast and Kernel tdsskiller to scan for viruses and malware. It all came back clean. Can it still be a virus or the like?
Used Wise registry clearer and Ccleaner but noting alarming came up, (Again i think.) some things yes but smashing the `fix all´ button did not fix the cpu issue.

First i though its my GPU drivers causing the problem. (said google) Around 45 days a go replaced my old AMD 6950 to a new AMD Radeon R280. Allworked fine till now. I found out that according to Unknown Device Identifier i had the old drivers still on my machine. I had issues removing the old drivers but ultimately i had to use a Display Driver Uninstaller to get rid of them and now i see only one set of drivers. This did not fix the cpu usage issue.

Im lost, at the end of my skills (mainly google-fu). Can anyone help me? I hope this is the right place to post this, if its not then i apologize.

If and when you (hopefully) want me to post logs and whatknot please first tell what program to and where to get it.

Motherboard 790GX-G65 (MS-7576)
CPU AMD phenom II X4 965
Video card AMD Radeon R280X XFX 3GB DDR5
Monitor BenQ E2420HD LCD 24" 1920x1080 resolution 75hz
RAM 8GB DDR3
Power Supply Thermaltake smart series M85OW eu

[_I_]

if cpu usage is maxing 1 core (or equivilant spread across multiple cores)
and its usage is not showing up in processes (with all users ticked)
its most likely a driver issue

disable windows driver updates
http://technet.microsoft.com/en-us/library/cc730606%28v=ws.10%29.aspx

and get the latest drivers from msi/amd
http://us.msi.com/support/mb/790GXG65.html#down-driver

[[M.V.P] VolcanoHigh]

Did what you suggested, i had already turned off/disabled the windows driver updater.

I also updated all the drivers on the manufacturers site concerning my motherboard aside touching the BIOS and On-Board PIDE/SATA Drivers. Updated my On-Board Audio Drivers, On-Board LAN Drivers, System & Chipset Drivers.

So far at the time writing this no problems has shown up, all works fine now. Procexp says System interrupts are now less then 2, compared to the earlier 20-25 this is a sign the updating fixed the issue. It seem that this fixed everything.

Thank you, now i dont need to fantasize shooting my computer in the proverbial face.
I have learned something thanks to you.