Hi, I have a ColorPro plotter and I got it work just fine.
First you need a 25 pin to 9 pin serial adapter. Then use a NULL Modem cable going to the PC.
I found that if you can save out *.PLT files from your CAD software, you can send them directly to the plotter from a DOS command prompt (yes, even in 2K or XP) by doing the following:
1. Open a Command prompt
2. Type "mode COM1:9600,N,8,1,P"
3. Then type "Copy <path and filename of *.PLT file> COM1" and press enter
This sends the plot file directly to the plotter.
Myself, I've written a small bit of software to handle showing me a preview of the vector drawing on the plotter (HP plotters are 1100 plot units per inch or something like that)
-niko