What I want is to be able to store data in the 500GB disk and operate from the 320GB disk.
Sorry but you have messed up here you should not have even gone never RAID the fact that Rapid Storage prompts you is that you where ask if thats what you want not that you had too you should of cancelled and formatted the drive as normal. Now you are stuck with RAID 0 unless you delete the array and reinstall your OS.
So now thats out the way here is what you have done and what is RAID 0....ok let say you make a txt file with “THE END” in it what RAID 0 does it puts “THE” on one drive and “END” on the other ...that is now done to your whole OS and files! If one drive dies all your data is lost.
And now thats out the way too why 610 GB (really 640 GB and not really 640GB due to 1024KB being 1000KB on disk...never mind...) this is to do with what I said above and your ST9320123AS … because you had 320GB the max array in a two disk RAID 0 setup can only double the size of the disk you had.