Just wanted to let others know that I installed the PCI-e PathPilot upgrade in an old mid 2007 Inspiron 530s I had sitting around (Intel Core2duo, 512mb ram, 250g HD) and it worked just fine. I have NOT milled anything since (just did it last night) but will update this thread with the results.

Although the instructions are to upgrade your existing controller, I did not want to chance hosing my working setup (which I need to do my work!), so I just grabbed this old PC. I still have the HP dual core machine (of about the same 2007 vintage) with XP and Mach 3 that I was using before and can just swap between the two until I'm confidently fully transitioned.

Setup was easy. Just popped in the CD, pressed F12 at boot to boot from the CD. It asked me some stuff and flashed an image to the hard drive. Afterwards I had to select the Series 3 1100 from the list of machines. The interface card's firmware was updated.

Two hiccups:
1) the machine no longer turns off without pressing the physical power button. Also, the Tormach screen that comes up and asks you to reboot the machine is white text on a mostly white background, so it's impossible to read the prompt, also it says something about shutting down.
2) the card is made for a full size PCI-e slot, although it's physical size is small enough for the Inspiron's half height computer case. The L shaped bracket that secures the card to the case does not fit with a slim form factor desktop machine. I used one of the blanks that came with the Inspiron case and dremeled a hole for the 25 pin port and drilled holes for the cable screws. I had to use an entire cut off wheel though

Hardest part was that I had to wait quite a while for the part to be in stock @ Tormach -- it's probably easier to buy crack around here than the PathPilot PCI-e upgrade...