I just felt like making note of my own successful fan install, with the help of my father, formerly an electronics assembler. Used a bit of wire with a pin connector from an old case that had front panel USB ports, and some heat shrink tubing. My father did the soldering, of course. Then I slid the connector onto one of the fan pins, and looped the ground wire under one of the ground screws. I mounted the fan with some small rubber grommets, which i trimmed as much as possible, and good old Krazy Glue. I folded the IDE cable underneath the drive tray, and slid the top cover back on front first, in order to avoid putting vertical pressure on the capacitors on the display board.

To my knowledge, the noise from the fan is purely wind rush; no vibration. It's not exactly quiet; but then, my PC is so loud (still) that it doesn't matter. As for cooling - I originally chose to do this because of the empeg reaching high temperature in my Civic during the winter. Now, after some use, I have found that either on my desk or in the car, it never tops 31­°C.

BTW, I used a 40x40x6 millimeter ADDA fan, first mentioned, I believe, by Legoverse in this thread.

Not having a digicam, I don't have pics just yet. But maybe I can convince my sister to let me borrow hers and work up the bravery to unmount that top cover for some. Thanks to all who answered questions and provided links.