I too use Win Xp, LT '07 and HP 500. I've used the OS and plotter since LT '04 and had no problems. I've never replaced a print head either and get very fine plots.
I did order the plotter with the ram maxed out and I think that is still a good idea.
Just my 2 pennies...
Oh, it is connected to a small network, FYI.
mg