any computer gurus here?

You have to start over with a fresh install for striped RAID because it needs to distribute the installation over two drives.

With redundant RAID you can just tell the BIOS to "Build RAID Drive" or whatever wording that machine uses.

So yes, a reinstall is necessary unles something has recently changed.

www.bootdisk.com is where you can download a file to make a bootable disc.

If you have a factory image one the original drive it can be copied to a DVD or USB drive and that can be used to reinstall with, but you would need to look up how to make the disc bootable for that.
The info is on the net and I can't remember all the steps off the top of my head.