Nevertheless, many (if hard-core) PC owners will have an old power supply lying around (you know, the ones that worked with your Pentium1 / II processor?). This instructable will inform you on how to extract the (typically silent) fan and convert it to run off the motherboard's fan ports.
Step 1: Step I: Extracting Your Fan
You're after the fan, anyway. Unscrew it from the case. Cut the black and red wires at the board (not close to the fan, you want these) and use a wire-stripper (or as dad taught me, teeth work in a pinch, though not an entirely good or clean way) If your fan looked anything like mine (probably will) you might not want to use your teeth, and DO clean it with a large-ish paintbrush. (no water, trust me on this one)
Step 2: Step II: Soldering
Before they're soldered, make sure you have heat-shrink tubing along them - one for each cable and one wrapping around them both / all three. I just used tape (not safe)
Now, with all the wires stripped, solder them together. Don't worry about the White cable if your fan doesn't have one. it's just a speed-control one and it still works regardless. If you'd like, use blue-tack to hold the wires/components in place.. it's cheap and functional, I've done it for years XD
Step 3: Step 3: Testing and Finishing.
fasten it to an empty case fan holder using the screws from the PSU that were holding it in place.
Go ahead and turn it on! If it's a bit noisy, just add some sewing machine oil! (I didn't have heat-shrink tubing so that's why there's lack of in my instructable)
Enjoy your new lower temperatures, hehe.