After installing Firefox 18, Firefox 15 still shows in "Uninstall"

After installing Firefox 18, Firefox 15 still shows in "Uninstall"

I recently updated to Firefox 18. If I go to Windows' Control Panel and then click on "Uninstall a program", both Firefox 18 and Firefox 15 show up in the list of programs. Should I just leave it as it is, or should I uninstall Firefox 15?

By the way, I updated to Firefox 18 through Firefox's update feature, if that helps.

To the best of my knowledge when you installed Firefox 18 it should of removed older versions. I have updated Firefox for years and have never had to remove the older one. If Firefox 18 works as it should I would think that removing the older one should not hurt anything.