I use a RAID 1 set for my production work and other important files.
I'm going to increase the size soon though from 120G to 500G cause space is limited.
What i'll do is get two 500G drives RAID 1 them and move all my files to that array.
Then RAID 0 the 120G drives to get 240G for OS and programs.
@OP: Your motherboard chip-set supports RAID and it's simple enough to set up. Just decide what array you want.
RAID 0 will give you a theoretical increase in read/write speed but if one drive fails then the information on the other drive becomes useless!
RAID 1 will give you data redundancy - If one drive fails then you still have the same information on the other drive. Although read/write speeds can be a little slow. But to be honest I haven't noticed it.
RAID 0+1 is a combination of the above and will in theory give you the increased read/write speed of RAID 0 and the data redundancy of RAID 1.