I finally went down to my old MPL office to pick up the 4 year old P3-800 server. It's been offline for awhile and I realized I needed it now because it's the only machine that still has my private gpg key.
While I was at it, I also transplanted the server's hard disk, floppy drive and a case fan to my P4 desktop. I also picked up an Enermax double ball bearing case fan with manual RPM (1000-3000) control.
So now, the P4 desktop has two front inlet case fans directed at the 2 hard drives and a little wire dangling out of the front usb port enclosure. It's pretty fun manually adjusting the fan speed, seeing the RPM numbers climb in GKrellM2 and hearing the decibels.
Now I just need to get my hands on some case fan spacers, specifically the Acousti AFG80C Anti-vibration Silicone Fan Gaskets or Gel Fan Mounts.
Here's a useful link that shows proper airflow.