yeah i actually stumbled on those on cnet last night after posting this and it worked...im not afraid of killing firefox, whats the worst that could happen, ill have to re install firefox? oh well. but yeah, those actually do work. thanks.
I think it could corrupt or delete your profile, where all the bookmarks are stored. You never know with Ad-Ons, what they can do with the browser being tweaked to a different version.
There is MozBackup to save your FireFox profile. It's great when you have different machines, so you can just backup a profile and then install that profile onto another machine.