JScones, you might want to try the Nvidia 84.XX series of drivers by all accounts from both overclocking sites and regular Nvidia sites they are the best drivers that Nvidia have produced, I have a 6600GT I'm using a modified driver from the site mentioned above called Ultraforce 84.66 "Sedona" on my machine I have a big upsurge on FPS on most games I play See this thread :
http://www.subsim.com/radioroom/showthread.php?t=93360
Hilis Hatki, I'm sorry you are having this problem but from what you are now describing, is a much more serious error than getting SH3 to run, As to getting your copy of Windows back to 100% order. If you cannot download Dierct X which is a certified windows product, I can only see one real course of action, which I'm sorry to say is a re-install of windows product, you might want to try putting your windows cd in and letting it boot up. I think also there is a "Repair" function after you hit install windows , this would then just scan your system files and hopefully repair whatever errors you have.
Sorry to not help you further but I aint no comp whizz (I know just enough to get by)
Deep Six