If you have an Asus board you can run PC Probe ( good name, eh?) and get your temperature and fan rotations ( if they have a rotation [green ]) wire hooked up. My basic boring system (PIII 1GHz) is running at: CPU 29'C, MoBo 25'C, with Ambient air temperature 20'C in an Antec SX1030. Around these parts the Antec 1030 costs $150 Cdn ($100 US) so it isn't much more expensive than a crap case tm, and it has a good 300W power supply, which I think is about right. Perhaps your power supply isn't cranking out enough juice, but probably that's only part of the problem. My drive has always run very cool, Maxtor DMX Plus 60 7200/40Gb.
I actually go to the extent of using the ribbon cables as air scoops so that they direct the air blowing in from the front across the drive, and then up across the CPU and out the back fans.
I'll know I've gone too far when I cut up a plastic supermarket bag into a fringe and tape this to the back of the case near the fan outputs- so it sounds like the breeze blowing through palm trees.