Existing RAID0 disk in NAS?

You would need to put them into something with the same controller and software drivers. Find out what chipset you had in the bad PC, and find another PC with the same chipset and BIOS.

How did you build the RAID array? Were you using software fakeraid or Windows RAID?

If its in a PC, then there should be RAID BIOS you can get into, usually with CTRL-I during boot.
You then delete the existing Array volume, and create a new one with whatever RAID level your want.

I changed my RAID0 to RAID1, by using Active Disk Image, to back up the existing array, then did the above, and restored the image.
I then had to run Win7 Startup Repair once from a CD, and then ran the iastor software in Win7 for it to verify both drives under RAID1, which takes about an 1hr for 500Gb.

That probably rewrites the volume GUID used during the boot sequence, because as soon as I restored the disk image, I was able to explore the entire RAID1 drive, befoer I ran Startup Repair.