Please post specs of your motherboard. If it is raid through the motherboard, you most likely have what they call 'fakeRAID' which is really software raid under the covers. Anyway, Ubuntu clearly states they don't advise installing on fakeRAID
, but here is a link to a howto on their site:
It's a bit daunting only because the page is so long, but I think you only need to worry about the install portion.
Hope this helps! Good luck.