Hi luddite Biggerdave, :-)
Windows 7 is as rock solid as xp and 8.398, my advice should you be tempted is partition your harddrive in two so you can add win7 or better still buy a fresh harddrive to put it on, both methods will give you the option of booting into windows7 or xp on start up, this way you gain but dont loose as you will always have a spare os to boot into should one go wrong, i have xp, 7 and 8 to boot into on a 1 terrabyte drive, you can add a new os in addition to an older os but not the other way round ie, win7 first then xp for instance, this of course wont be a problem for yourself as you already have xp installed.
jazz.
;))