Hi
I had the same problem myself. I started to think that it could be some drivers from motherbord disk.
So I formatted my hard drive then i installed de drivers from the cd one at the time to see if I was right and I was!
I have a GA-K8N PRO-SLI and it was the driver for the IDE from Nvidia
I installed only the chipset and audio driver without the drivers for USB and IDE that came from Nvidia and now my hard drive is no longer safe to remove
If you have this problem try to instal the drivers for the motherboard cd one at the time to see were's the problem
I hope it was useful