I configured Windows XP (with a hack) to run software RAID 5, which is cheaper than hardware RAID, easier to move to a new system (just plug them in and select them all in Device Manager and reenable), and the speed is plenty for my uses – CPU usage is <3% with an Intel Quad Core 6600.
Next steps are to create an automated zip, encrypt, and offsite backup to a hosted FTP server 5 states away..
