I would guess its on PIO mode instead of DMA. I had similiar problems... PIO is about... 10 3 times slower than DMA which can make your devices feel really slow... Here is a quick way to check... go into your device manager under IDE ATA/ATAPI Controllers;



then go to properties of the controller you have the device on and click the advanced settings tab. Change it from PIO to DMA if need be;


Lemme know if this works. 95% of the time I hear about this problem, this is the solution.


EDIT; to give you an idea of the speed difference between PIO and DMA here is some rates from one of my X86 hardware books:

PIO;

PIO Mode 0 = 3MB/sec
PIO Mode 1 = 5MB/sec
PIO Mode 2 = 8MB/sec
PIO Mode 3 = 11MB/sec
PIO Mode 4 = 16.6MB/sec

DMA;
Ultra DMA Mode 0 = 17MB/sec
Ultra DMA Mode 1 = 25MB/sec
Ultra DMA Mode 2 = 33MB/sec
Ultra DMA Mode 3 = 44MB/sec

These are the theoretical peak speeds, but they will NEVER achieve these speeds or even 60% of these speeds for longer than a few milliseconds. 

Windows NT 4.0-6.0(vista) usually toss out most configurations made by the BIOS and use its own. That being said what you do in the BIOS wont affect it(shouldn't atleast)

So if you set it to "DMA if available" + restarted windows and its still on PIO that probably means all your DMA(Direct memory access) channels are in use.

My knowledge of DMA is a bit dated since the last time I ever had to any in dept configuration of them was back in 97. However, back in those days there were 8 DMA channels (0-7). I bet there are more now, but eitherway I bet you just have to free one up. Go through the list of you controllers and see if you cant find something using DMA that you dont really need to be that fast. Change it to PIO and let me know what happens

Heh, no problem! Glad I could offer some help! Lemme know if any other problems arise...