Do you want to raid them for performance or redundancy? I have to say that I would never trust my data with a windows based software RAID array.
If you want speed and redundancy with that number of disks I would suggest going with a RAID 5 array.
RAID 5 will yield you the space of the number of drives you are using, minus 1. so if you have 6 250 gig drives, you will get 1.25 TB of usable space. If one of those drives fails for whatever reason, your data is safe. if 2 fail, you're fucked.
You will notice a significant performance gain with each drive that you add to an array. I have 12 7200 RPM 2TB drives in RAID 6 (# of drives -2 for redundancy) and I get around 650Mb/s transfer rates, and the redundancy of being able to lose up to 2 drives at once without losing any data.
I have a dedicated Adaptec RAID controller that takes care of all of my drives, while software RAID is very efficient in UNIX, I wouldn't bother under winblowze. UNIX OS's are far more stable and rarely need to be restarted or lock up. One BSOD could result in data loss if your drives are being written to or accessed when it happens.