It honestly should have worked. Windows just sees it as a generic card. Strange that with ram replaced you still have errors. It may help to remove, disable any other hardware(USB/Comm ports/sound) for the install, but not normally required.
Have you tried each stick to see if one is stable?
What version of Windows are you installing anyway?
Unfortunately, many things can cause this problem.
-Bad ram(you cant fix it). I had this with a 4200ti card, nothing I could do, but it was under warranty so it was replaced.
-Bad GPU core(you cant fix this)
-Bad power, but if it does it in more then once system. its not likely this
-Heat. You can fix this, but it looks exactly the same as bad GPU core so is hard to trouble shoot unless you can get the cards temps.
-Core de-soldering. Very doubtful, but that would be the only reason to bake the card.
-Drivers. almost impossible in this case.
The worst part is that AGP cards are far and few these days and overpriced to hell.
Your temps do not look out of place. A load temp would help, but if you are crashing, you should log it with GPU-z so even if you crash the temperatures will have been logged(2 bottom check marks and select a easy to get to file location to log to).
If you are not overheating, the card may be going bad. Not much you can do, you can try to make it, but the 6600's did not seem to be a card that has solder issues requiring that fix.