I'm in the sign business, so most of what's being discussed here is beyond me, but I do have a fascination with old plotters and computers. I have an operating HP7596A. I saw a posting about that model in the archives. This is what I've learned about it: Cable must be specific for that model. Pin#20 is critical, without it, you get buffer overflow. I bought a CD from ebay that has 3 manuals on it. Real handy. I already had the paperback user's manual, but the other two are more detailed about error codes and maintenance. I was surprised to see that Windows98 still had a driver for that old plotter, but the friend that told me about it said there is a better driver from Winline. I was told that the Roland company copied some of the technology for their sign plotters from HP, so much so that the pens are interchangeable. All I know is that the pens I bought for the HP fit perfectly in the Roland (pnc1100), and I didn't need to buy a swivel knife for the HP, as the one But don't get any bright ideas about newfound wealth from the sign trade. Ha! SATURATED market. Somewhere, but I can't remember, maybe hidden in the HP site, is an interchange list, that tells what parts are interchangeable with other models. Real handy for buying off ebay. I bought this plotter from a HUGE place that was being built near Crossville Tenn. USA. They said they have the ability to break down and recycle computer parts. They put whatever looks useable up for sale. Worth looking into?