couple things that should help your headaches.
1> Buy WD Raptor drives. They have better bearings, better heads, better everything really. They're meant for constant server use, and are rated at a lot of hours. Also 10,000RPM vs the normal 7,200 so the extra speed is nice.
I use one as my OS drive, where I keep my most important information and install programs to it.
2> If you use a lot of drives for storage, consider RAID. If you only use one drive as a repair drive, you only dedicate one out of every 4 drives.
3> Use PerfectDisk to defrag, it's nice.
4> I'm looking at one of these myself.. You can get a 4-bay hot swappable rack system, so you don't need to keep your drives online and humming at all times. Just pop them out at anytime, while the computer is running.
http://www.tigerdirect.ca/applicatio....asp?CatId=285