(1) You need to do a re-install of operating system to convert to Raid0. Selecting Setup raid0 in bios will wipe out the partion data on your current HDD. Which means backing up your files and data and reinstalling your programs.
(2) Normally (not required) it is best to use two identical HDD. Your Current drive segate -10 is a discontinued model.
Then, buy 2 new identical HDDs for your RAID 0 array;
enable RAID mode in your BIOS;
enter the Intel Option ROM
and add those 2 new HDDs to a RAID 0 array; then,
restore your drive image to that RAID 0 array.
If you've done everything correctly, you should be able
to add your Seagate as a non-RAID member, using that Option ROM; and,
you can read your drive image file from that non-RAID Seagate HDD
when you restore that drive image to the new C: on your RAID 0 array.
Finally assign your existing 320GB Seagate to data storage / backup duties.