xcopy *.* c:\destination_folder /e /c /i /f /h /y
sc stop wuauserv
shutdown -m \\computername -s -c comment
net start wzcsvc
chkdsk /f
first, try removing through the add-ons menu, and try add/remove programs in control panel, if that doesn't work:
1. close firefox
2. do a search for 3112ca9c-de6d-4884-a869-9855de68056c
3. make sure you have checked to search for hidden files
4. destroy all instances for this folder
5. restart firefox and it should be gone