Hard Drive Access causes computer to slow to almost Hault

Hi, I recently bought two if these drives for my machine but i am having trouble with both. When accessing the drive, it will run ok for a while, and then all of a sudden the system goes so slow that it only refreshes ever like 20 seconds. And if i hard reboot, the harddrive disappears from my bios and i have to unplug and plug it back in for it to show up (when the power is off of course).

The drive was formatred to a single partition in windows vista ultimate (x86)

Mobo is an Asus p5n-e sli

PSU is OCZGXS700 (OCZ GameXStream 700w).

Tried with two different sata cables and two different leads from the PSU. Both drives do this! Also, my previous HDD was a 320gb sata aswell.

I have not set jumpers or fiddled with anything other than doing an error scan on HD Tune Pro

Thanks for any help!


PS: I wanted to add that i've tried the drives in XP as well (same thing), and that all processes seem to go to 0% when the slow down happens (had task man open)

Heres some pictures of the sats settings in bios (as someone thought it might be that)

http://i55.photobucket.com/albums/g127/LordVishiscat/helpme/IMG_0240.jpg
http://i55.photobucket.com/albums/g127/LordVishiscat/helpme/IMG_0242.jpg

Well, I don't pretend to be an expert on this stuff. But if your previous hard drive worked and the new ones don't, I'd have to say it might be an issue with the new ones. Maybe return them and try a different brand?

Wish I could be more help.