I'm going to be setting up a little server at work for sharing CAD files and handling some PDM issues.  The number of regular users will be <10.  I had been thinking Raid 1 with two 1Tb drives, but am now leaning towards Raid 5 with 3 500Gb drives.  Both configurations give me 1Tb total storage with single disk failure protection, and Raid 5 should perform better.  Anyway...

I'd like to leave the OS on a seperate drive that is not part of the Raid configuration.  Then just the data will be on the Raid disks.  If I need to wipe the OS, it doesn't affect the Raid disks.  Is this a good idea?  The only disadvantage I see is if the bootable drive fails, I'll be down until I replace it and get the OS reinstalled.  I should be able to add the Raid disks without messing with the OS, correct?  Should I leave the non raid disk connected to the MotherBoard, or plug into the Raid card (and configure it outside of Raid, if possible)?

More (possibly superflous) information:

• I'll be using an Adaptec 2420SA controller
• I'll be getting a new XP Pro machine
• Dual Core Xeon 2.4's
• 4Gb Ram