You are aware that the 5800 was deemed a failed product aren't you? Nvidia rushed the 5900 out onto the market to try to get their reputation back. The overheating is from the core speeds on the card being too high for the card's fan to handle no matter how big, loud, and fast it is. Take it out and put it on Ebay. Take the $$ you get and invest in an ATI 9800 Pro. You'll be able to take out the case fans and your cpu temp will drop a good 10C.

Also, look into some liquid cooling, a P4 at those temps is WAY too high. It should be running next to cold. My AMD system on full load only runs at 50C, and is 44-45C idle. You're going to have to kill this heat if you want to survive.

I have 1 side fan blowing in, 1 hdd fan blowing in, and 1 grill fan blowing inward. I have 2 exhaust fans in the back (PSU fan makes 3) pulling the heated air out. When I close my case, I see a 10C drop. Maybe you need to strageticly place some of your fans to vent the air out, so they aren't all blowing inward as that will kill airflow because none of the hot air is flowing out. My personal design/placement is rather quiet. My exhaust fans are controlled by my PSU/Motherboard, so they stay nearly quite. My Hdd fan is controled my my Vantec fan speed controller, so if it gets too loud, I can just drop the noise level down w/o sacrificing airflow. Only my radiator, video card, pump, and grill fan run at full speed, so I only have about 40-45dba of noise, and I can control how loud I want that.