I have 3.0 sata connectors on my mobo.
I do alot gaming and am running Vista 64
The HDD need not be super huge - 200gb would be fine but Im flexible.

Any suggestions for under $200? ...or there abouts.

Also - is what is the he best determining factor for a 'better' hdd?

Currently I have two older 10k 75gb raptors in a raid 0. My raid controller software is telling me one is failing, although it is still working - but i have been getting crashes and blue death screens.

If one of the Raptors if failing, then WD should replace it for you. Those have a 5yr warranty. I'd stay with Western Digital when getting other HD's. They have good support, great diagnostic programs, and just seem to be the preferred choice of many. I have 2 Raptors, 6 External, and 2 Internal. All are WD. Never had one to go out.

http://www.westerndigital.com/en/p [...] anguage=en

Fastest thing round and should be ~$200 i believe.

If you could wait a couple of weeks and stretch the budget to around $300 a velociraptor would be my choice.