High CPU usage, System Idle Process @ 99 ....????

Problem solved! I decided to reveal how given how many high CPU usage threads there are with people claiming System Idle Process was at 99%. Turned out to be a problem with hardware interrupts, which is either related to a driver you're using, or an actual hardware failure. Found it by using a program called Process Explorer to further inspect my processes. Used a program called RATT to actually see what was requesting so many CPU cycles. I checked the log RATT created for a column labeled IRS, which showed one file requesting a staggeringly higher amount of CPU cycles In particular hdaud.sys had to be disabled. Set the driver to disabled in Device Manager and the problem no longer persists. If it continues to persist after being disabled, then it is likely a hardware problem and need to reseat components and check their integrity through tools available from their manufacturer.
450 Watt PSU
2.0 Ghz AMD 3200+
Gigabyte K8N Mobo
512mb Corsair RAM x2
HIS Radeon 4670 AGP
XP Home SP3
Western Digital 200gb x2

Yesterday I woke up to find my computer was off, due to a power outage. CPU usage is now idling at around 30-50%. I checked the process tab in task manager to find that nothing was using my CPU, and that System Idle Process was at 99. This should mean nothing is using it, yet the high CPU usage remains.

Prior to this my computer would often idle at 2-4%, only reaching about 50-60% when running Call of Duty 4, and 80% when running Starcraft 2. I noticed in both games with the graphics on low that I was getting around 30 fps, whereas I normally get around a steady 60 with medium settings. Interestingly enough, my ping to nearby servers was up 20-30 ms which has never happened before. Ping increase was also present at speedtest.net

Scanned using Avira and Spybot, found nothing. Uninstalled Avira, checked with AVG, still nothing.

Checked MSConfig, most of startup is always unchecked, in services there wasn't anything new.

I run my OS partition very lean, so reformatting was a quick answer to try. Surprisingly it remained at a consistent medium usage despite the fresh install.

I've tried googling various terms and have come across many with CPU usage problems, but my situation hasn't been answered by anything I've found.

So I turn to minds more experienced than my own:

Is there a program I can use to break down CPU cycles more completely?
Is there a way to test if the power outage has partially damaged the CPU, without another computer to test it in?
Are there other plausible explanations for this behavior I'm unaware of?

Screenshots of my task manager processes and performance tab can be found here:

http://img413.imageshack.us/i/wtm1.png/

http://img690.imageshack.us/i/wtm2.png/so

Nothing different. This is the confusion. Everything looks normal from the processes view, my CPU is idle at 46% right now, with 10% usage by firefox shown in the processes tab with 'Show processes from all users' checked.

Sort your task manager by CPU usage (with processes from all users shown), then take a screenshot of it. That's probably the fastest way for us to see what's going on.

quit same problem.
havnt played sc2 for 1.5month,
came back home,
updated all the patches,
and after i enter pass and login i get 98-99% cpu ussage from sc2.
pc on idle shows 98-99%.

updated newest video drivers, same.
amd 3400+
2gb 530 ram
gf 7600gt
previously worked good.
i gues its the problem somewhere with patch