ICH10R on PQ5Deluxe RAID config on Win7 - Can't add disk

I have 4 1TB drives.  Currently running a RAID 0 volume of 3 drives and 2TB (rest unallocated.) These are WD Cavier Green drives.  Also have a Segate 1TB drive (exact same specs.) and want to add it to the Array.  No option in Matrix or Rapid Software.  On boot it says its a non-member disk. My goal is to run all 4 drives in Raid 10 (I hear raid 5 is slow / buggy).  I've tried everything to add to array or create a new volume, but it won't let me add!  I have BIOS not EFI but only want a 2TB volume - not sure why I can't add a 4th drive.  tried several versions of Intel ROM/Software.

Should i just reset drives and rebuild?  Why can't i add the Segate drive?  Will i lose data?  Any other config suggestions???

Thanks for any help out there.....

S.