Are you talking about older Firefox versions that appear in the Windows Control Panel > Programs?
If there are multiple versions of Firefox in "Control Panel > Programs" present then it is likely that you only see orphaned Firefox entries from older versions and that only the current release is really installed.
This can happen if the Firefox updater didn't remove the entry of the previous version, but merely added an entry for the new version.
If you uninstall such older versions that are actually no longer present then you will likely uninstall the current Firefox version and you will have to reinstall Firefox.
If you are comfortable with the registry editor then you can remove Mozilla Firefox entries that no longer apply in the Uninstall registry key.
If you have a 64 bit Windows version then inspect this key:
HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Windows\CurrentVersion\Uninstall\Mozilla Firefox (????)