System spec and Mach3

[gorbo]

Of course, both same software

[Jonathan]

Of course, both same software

Just to clarify...
If you installed the demo version on both PCs (or your licenced version didn't install properly) then it would not limit the lines on the home PC since either it doesn't have a parallel port or you didn't install the parallel port drivers. The 500 line limit is only imposed if mach3 is sending signals to the port.
That could explain what's happening. Check to see how many lines of the code it it loading? Or press the start button and see if it gets stuck at 500.

The computer I'm using for CNC is an AMD 1.4ghz, with 1gb (might be less) of RAM. Never had a problem loading over 100000 lines, though I can't use more than 25khz kernel speed.