You didn't say what he was using as a controller. If it's onboard then get the chipset info on the board and the controller hardware/software to see if the array can be transferred without any glitches. If you're going "like to like" then it's usually not a problem.
Note - I noticed that none of the subject matter experts jumped in yet so I was just helping lend some direction on this one.
From what I can gather, he's using the onboard controller (no add-on card). I wish he had told me that it was in a RAID 0 configuration before I had started - I would have noted which exact SATA ports his HDD's were connected to. But I didn't pay attention to it
Piratepast40 is right, like-to-like usually can be done. I know all recent NVIDIA chipsets claim this is not problem within their line, but the mobo you're dealing with has an Intel ICH9R southbridge chip. Check what Intel and / or Gigabyte has to say, by searching their websites for a detailed manual of how to set up and use their RAID controller functions. Or, if you're lucky, the info might actually be on a CD that came with your friend's mobo originally.