I believe it is on its third set of mirrored hard drives now. The original video card and power supply have been replaced, as has one of the case fans and the heat sink fan. The memory card reader stopped working some time ago and I never bothered to replace it.
Heck, this thing still has a floppy drive.
All that said, I originally built it out with a quad-core Intel i7 chip and 4 GB of RAM and those have, thus far, proved sufficient for my needs.
Here's hoping I don't need to build a new box for quite some time. :)