I don't know about uninstalling zone alarm to put Sygate on, but if you're going into the registry, then before you do anything click file, export to save the current registry. I usually place backups on at the root of c: so they're easily accessible. You should be able to restor it by doubleclicking or right clicking and selecting merge.
Try Reg cleaner from click here it's easier to use than the windows one, and any keys you delete can be backed up.
Sorry I can't be of further use, good luck. And if you're unsure if a key is what it's meant to be, don't change or delete it. Any problems and post back, there should be someone who can help prettty speedily.