Windows 7.
had onboard sound...but it didn't work with my 5.1 speakers or 5.1 headset...
Put in my old 10 year old card for those...and I guess it's kinda dying.
Figured a card is only $70 or so...(40 quid) so cheap considering the $$ and everything I've put into the game so far (4 computers, 2 trips to UK, 3 monitors, 8 or so video cards, being drugged and raped by Painless while in UK, trips to see BG, getting a tree for anniversary because of jealously over the game and so on...)