Thanks for your update.
A quick bit of googling suggests that the free version of Revo Uninstaller will remove Firefox:
http://www.revouninstaller.com/revo_uninstaller_free_download.html
The normal way of uninstalling (via your control panel) leaves your personal profile (with your bookmarks, etc) untouched, so that when you reinstall Firefox you get back everything that you had before. That might still happen with Revo uninstaller but, to be on the safe side, I'd recommend backing up your Firefox bookmarks first, as follows:
Press the Windows key
Type 'places.sqlite' into the search box.
When you see that file listed above the search box, right-click on it and select 'Copy'.
Go to any convenient location (such as your desktop), right-click and select 'Paste'.
If your bookmarks don't reappear after reinstalling Firefox, click the Windows button and search for %APPDATA%\Mozilla\Firefox\Profiles\
Double-click on the folder shown in the results box to open it.
Delete places.sqlite from that folder and then replace it with the old version.