Annoying but not unexpected. You write you have a lot saved from Mozilla so any content or files are safe in what download folder you used.
Even if you reinstall Mozilla I've always seen it use the old Firefox (if that's what you call Mozilla) profile. Use any working browser, head to Ninite.com, check off the Firefox item, Get your Ninite, run that and let it reinstall Firefox.
I did a system restore and now cannot open Mozilla. This application has failed to start because its side by side configuration is incorrect.,Please see the event log or use the command line sxstrace.exe tool for more details. I have no idea what that means. It is an HP laptop M7S72AV with windows 7. I have a lot saved from and on MOzilla..Please help