I've been trying to enable some sort of frequency scaling on my computer with no luck. I'm running Ubuntu 8.04 on an HP dv5-1004nr with and AMD 64 Turion X2 processor. Since I'm using AMD, I know I need to use their Cool 'n' Quiet driver, powernow. I've tried lots of tutorials online, but nothing seems to work because my computer keeps telling me that it doesn't support frequency scaling, which I know isn't true since I definitely was using Cool 'n' Quiet when I had Vista (and my computer is extremely new, so it almost definitely would support CPU Scaling).

Anyway, the main problem is that the folder /sys/devices/system/cpu/cpu0/cpufreq doesn't seem to exist. In fact, I have no cpu folder in my system folder. I'm certain that is the main problem. Considering that, what would I need to do to enable some sort of frequency scaling driver? My computer has been running pretty hot and loud (and the battery life has been poor), so I was hoping this would fix it.

That is a known issue; allowing users access to CPU frequencies was considered undesirable but the whole thing was reconsidered for ubuntu 8.10, where you can switch modes on the fly with a simple click. In order to make it work on hardy, you will need to install cpufreq-utils and set modes from the command line; not nearly as flexible as 8.10 but it works. As always: detailed instructions on google.
Note: this limitation affects only gnome, if I remember well. If you install XFCE, you should find that you can switch CPU frequencies without a problem.