If I remember correctly, the GPS hardware with THIS VERSION of CoPilot is different than most other commonly used GPS units...it requires the computer itself to perform some of the calculations, and so can't be used with other software packages. This is part of the reason for the low price.
Here is a thread with more info on the software GPS issue.
And here is a link to Philips site discussing the software GPS technology used.
Just FYI in case someone was thinking of picking up a really cheap GPS unit... As long as it's used with the included software, this should work very well. I have CoPilot 8, and it is fantastic for in car navigation. The ONE downside is that the program DOES NOT integrate well into frontends...it can't be backgrounded or called to the front well at all. So, if you're content to run just Nav, then this is a FANTASTIC deal.