Slow but not slow? Please help!

I think I may be putting this in the wrong section but as I don't really know what the problem is I don't know where to put this. Please feel free to move it if you feel it necessary.

So, I have two computers. I purchased a 250gts for my main machine, got it, shuved it in, everything is fine. I took the 9600gt which was in the main machine and moved it to my secondary machine (replacing a 9500gt). This is where the problem formed.

In order, I turned the old machine on. I went into the Hardware Manager and removed the current drivers I used for the 9500gt (they were... 181.xx). Once those were removed, the PC restarted, and once it finished removing the drivers I shut it off. Popped the case, stuck in the 9600gt, and turned the machine on. Good. I went on to firefox and downloaded the most recent nvidia driver, 186.xx, installed it, power cycled the machine and turned it back on. Here I noticed the problem. Windows XP 32bit took over 2 minutes to load. Unusual.... I clicked on the WoW icon (yeah, world of warcraft) and waited....and....waited.... after far to long, it popped up the screen. .... odd, ok... something isn't acting right, it's going way to damn slow. So I go into Control Panel, System, and see if it's still running at 2.7, like it should, and it reported it was. Odd. So I pull up 3dmark06. Not even kidding here, it takes over a minute to load the first section.. once it starts going, boom 70 FPS, dipping down to 25 fps here and there. Well, ok, odd. Next scene comes up, the one with the whispy things. Takes over a minute to load, then plays the scene... 30-40 fps... weird.

So, at the end of it all... sm1 was like 4800, sm2 was 4200 and the CPU score was roughly 2500... ok.. those aren't the best numbers in the world, but it's what i was expecting.

So i figure, maybe i should run AVG (not that my spare computer does anything online other than WoW, but hey, you never know) seriously... the hard drive is use 35 gig out of 500 and it took 2 hours and 27 minutes for AVG to finish... yesterday it would have taken 15 minutes. wtf...?

So i spend 5 minutes waiting for WoW to load, get into the game and.............flawless. Everything set on max, running around getting playable frames............ ?

It seems as though anything that has to do with HDD access is slow? I guess? I didn't mess with that driver, nor did I mess with the IDE cable, so I don't know why it's doing that. I attempted to find an IDE controller driver but had no luck... so, I'm really stuck here guys, any help would greatly be appreciated.

Sorry the post is long, but I was trying to be as descriptive as possible and also vent some frustration.

The machine that is having this problem is only roughly 3 months old and the hardware is as follows....

CPU: AMD 7750be Kuma (at stock, no OC)
GPU: Was 9500gt, now is 9600gt currently with 186.xx (latest) nvidia driver (no OC)
PSU: Thermaltake Purepower 500w
Sound card: SB Audigy
MoBo: Asus M3A78 (yes i have the cd, yes i attempted to load the bios and chipset drivers, no ide controller though)
HDD: WD caviar blue 500g (long story why it's IDE and not SATA...)
OS: Windows XP32

All the listed components above are 3 months old or less, except the 9600gt which is just over a year old. I did check temps, and with Core Temp and Prime95 ... once they loaded ... it never got over 60c (Rocketfish HSF).

I think that's all... any questions, please ask, any comments, please, PLEASE post. I am so lost here and it is driving me nuts. It should not have been this difficult.

I guess I'd remove all nvidia and ATI software, and reboot.

If/when it runs slow, bring up Task Manager and check for high cpu utilization. Specifically, look for dumprep.exe running perhaps multiple instances. In any case, if high cpu utilization is doing this, what's eating the cycles will be a clue.

Could be a weak PSU problem. Probably a driver problem though. Of course the easiest way to find out is to do a clean install, but if you really just don't want too then download drive cleaner pro, remove the drivers, boot into safe mode, run drive cleaner pro, reboot, and then re-install the current nvidia drivers.

You could put on the RC of Windows 7...