Well I have 2 x Seagate ST3500418AS 500GB Hard Drives. When I'm trying to install win7 and I come to selecting the partition to install the OS to, there's nothing there. No hard drive, no unpartitioned space.
Hard drives are set for RAID atm, but it didn't work any other way as well.
All system is set up correctly and bios recognizes the drives and other hardware.
Try making them individual hard drives, like make it not a RAID config. If the RAID config is not in "mirror" mode, and one of the drives fail, the other drive can become unusuable and you need to format the good drive again