Can I setup 12 terrabyte RAID5 system using WIN2000 server or XP.

With that much data, its very hard to make a backup since that would require equal amount of storage.

Also, you need 48-bit LBA support to access all the space; Windows XP has this in SP2/SP3 i think; though your controller also needs to support it. If so you can just access the space.

But do know that large RAID5 arrays without backup are a serious risk. Not because of drive-failure but of corruption. If you want high reliability you should buy a battery backup unit (BBU) for the controller, or set write-buffer method to write-through, which will significantly lower the write performance. Without either, lost buffers during improper shutdown may trigger corruption on the array.

Good luck.