What could be causing this?

[Ridgerunr]

Does your case have an intake fan low in front? If so, those hard drives could be blocking it a' bit. I'd also suggest trying to get those flat IDE cables out of the way of airflow. If not moveable, you can double fold them between the connectors and use the nylon bundle ties(lil' ones) to secure them. This would improve the airflow. Looks like you have an upper rear exhaust fan below the PSU and that's a good thing.
Looks like you have an AGP slot for video, so the best choice for installing a card type fan would be on the opposite side of the vid card from the side it's fan is on. If that's possible. With your other PCI slots,i'd put the sound card(if not onboard,that is)in slot #3 and your NIC or modem card in slot #4 or #5. The more breathing room the better for the vid card. Looking at you hard drives again,,might be better if you could move the top one up to the next available spot for more breathing room there also...

[Yuri]

Ridgerunr, thanks for your post.
There is no intake fan at the front, do you think that I should put one there?
As for the IDE cables, I had thought about buying the rounded ones as they are suppost to be faster and take less room.
There is one slot above the video card and that is a AMR slot, since I have not been able to find a local store that sells AMR modems I might put a fan there to take hot air from there.
The only other expansion card I have there is the network cable and I put that right down the bottom.
As for the fan I have at the top should that be taking hot air out of the case or blowing cold air in?
Thanks once again, this is the first time I had to worry about heat as my last computer was a P2-450.
Yuri.

[Ridgerunr]

Hi Yuri,,Yes,,you definitely need an intake fan low in front. An 80mm with around 3,000Rpm should do the trick and be fairly quiet. Sunon and Panaflo are good brands. If your mobo has a 'case fan' connector,get one that has the small, 3 pin connector and the mobo will monitor the RPM's for it. If not(but most Asus boards do),get one with regular 'molex' connector and use a vacant one from the power supply. The fan below your PSU in the rear should be blowing out(exhausting). If you look at the sides of these fans closely,you should see embedded arrows showing fan rotation and airflow directions.
I use the rounded cables and have to say,they do a good job of letting the air flow thru'.
That 'AMR' slot is mostly for modems installed by the Mfg. and are pretty useless otherwise.
AMD systems 'do' run a bit warmer,but with a good CPU heat sink and fan and good transfer compound such as Arctic SilverIII between the CPU and heatsink,they run very well. Good ventilation through the case is very important and keeping it out of those 'cubbyhole' type desks so it can breathe is also a good idea...

[Yuri]

Ridgerunr, thanks once again.
I will go to the computer shop in the next week and buy a fan for the front, as well as the rounded IDE cables.
I also think that it would be better if I moved one of the two hard drives up another bay to let the air move around when I put the new fan in.
Yuri.