It's been a while since I've done it, but I think you may lose your project files, but not any saved avi/mpeg etc files.
You could copy the project files somewhere else while you uninstall, then put them back in Pinnacle's default project folder afterwards, if necessary. Not offering guarantees, but it sounds feasible. If you capture to Pinnacle's default folder (I don't) you could copy that as well.
Win XP, Athlon 1.8, G force 3 T, 1 60gig drive + 1 250 gig, Pinnacle Studio 9 plus mostly, Premiere 6, and Vegas 5 sometimes, Soundforge, Cool Edit.