To install windows, then set the first boot device as the CDROM and the second as the HDD. If you only have 1 HDD, then you dont need to specify HDD boot priority. RAID should not be used if you only have 1 HDD. Disable RAID in BIOS for SATA connector is correct.
Now put you windows install CD and reboot to boot from it. You may have to completly erase all the partition you created while you werre running you controller as RAID when you were using 2 HDD. Remember that RAID is not SATA. SATA is SATA and RAID is RAID. RAID can be use with SATA, SCSI, P-ATA too. RAID need 2 HDD. Repartitionning and reformatting is a good way to completly cleans the trace of previous screwed installation.
Now, if you cannot get it to work with all your memory, then in M.I.B., you can ajust the voltage of your memory. Try to raise it a bit. It may help with 4 dimm.
But if you try to start the old nstallation you did that has been formatted with RAID without being RAID, you'll likely encounter problems. A clean fresh start is the way to go here.