Win XP SP3 Causing High CPU usage, Slow Boot, Slow Performance

Can anyone please help? Is there a fix for this:

I do a clean install of windows about every 6 months or so...just to keep my system fast and clean.

Problems arose today when doing windows update to SP3.

Install Disc is Win XP SP2.
Nothing installed yet.
No drivers installed except for Lan adapter.

as soon as sp3 is updated. It becomes a big paperweight.
I thought I had a bad install so I reformatted again NTFS Full as I usually do.
And started over. install disc w/SP2 right away is Screamin fast as the day I built the machine.
As soon as SP3 updates from Windows Update.....Slow & sluggish.

Running intel P4 3.2 Ghz w/HT, 2 Gig ram.
XFX Radeon HD 4650 AGP 1GB

Task Manager shows 13 processes running
CPU Usage shows one of two virtual CPU at solid 100% pegged.

Is Microsoft Messing with us? SP3 was installing fine before, But I can't explain this behavior.

Please Help

Get the standalone "distribution" SP3 file, do not run from update. I never installed SPs from network and I never had CPU locking problems.

Ok I have still no solution, But thru different Forums some people are mentioning something about problems with the ATI Radeon AGP cards not playing nice with the system. Something about HDMI audio over AGP having issues. Apparently there is no fix that I can find. ATI Driver site has something called HOTFIX driver but that doesn't work to fix this. THANK YOU ATI for really testing this stuff out.

I have found that if I disable the "Microsoft UAA Bus Driver for High Definition Audio...my CPU Usage goes down to 0%.
However I have no idea if it's a good idea to mess with this. Anyways, It's always re-enabled when I reboot.

I HATE AMD/ATI right now. Spent good money on Tech that doesn't work.

Does anyone have a clear solution for this issue?