I got this program to work on ALL my PCs, with a little tweaking, including my Athlon XP 2000 (1.666Ghz). Just FYI, it has an Asus A7N266-VM (nForce1) chipset, with Award BIOS on pretty much stock BIOS settings. I tried the cable at 2 feet and extended it over 12 feet, still worked fine (I'm definatly using round shielded cable with serveral grounds mixed in, its 15 connector cable).
Loopy, what are the specs on your machine? Specs that might help include chipset, processor model and speed, BIOS (Award?).
Also, did you check your cable? I've found Brad's cable making docs to be a little confusing at first, and the connector doesn't look how he did it in ASCII. If you want I can post pics and more detailed docs.