Hmm it is from 05/06. I've actually managed to boot it in "ATA Combination Mode" - which I guess is just IDE mode (I think I exited BIOS without saving before when I tried that). Unfortunately this mode restricts me to use only 1 SATA port.
I assume the current Windows Installation doesn't have the SATA drivers. Is it possible to install them through the Start Up Repair suite Windows offers? Because I can boot into that in SATA mode.
UPDATE: Yes, you were correct! I found the correct drivers. I guess I'm going to just have to reinstall D: So much time wasted reinstalling + setting it up last night.
Thanks very much for your help sturm!