I recommend either getting 2 hard drives, or at least partitioning your drive into 2. This is very helpful because you can install windows on one drive and put all your data on the other, and if anything ever goes screwy, you can reformat the main drive and still keep your data! (I use C: as my apps drive, and D: and E: as storage and backup.)
Also if I were you, I would go with a 10k rpm hard drive as a main system and program files drive. These are mucccch faster than the normal 7200 rpm drives you may be used to and applications load much faster off them. It may be a little more expensive, but is worth it in the long run because applications that require more memory are always coming out.. and who wants to load them off a slow hard drive?! (My friend has a raptor 10k and a amd 64 bit 939 pin... he can reinstall windows in 5 minutes lol.)
Linky for Raptor 10k