That may be your problem. Norton is pretty inefficient and a crappy antivirus in general, and it can sometimes suck up enough memory to slow down programs like Toribash.
I would recommend downloading
Avira Antivirus and uninstalling Norton. Also: I know that after a full system recovery, your computer automatically starts downloading all of the updates that have been released since the computer's manufacturing date, since it loses any updates it has previously downloaded, during a system recovery. This is probably contributing to your lag, since downloads can slow down Toribash as well.
Finally, make sure all of your drivers are up to date- they may have been restored to their original states by the system recovery. Download the latest drivers for your video and audio cards.
^If you do all of this and see no changes in TB's performance, try opening up task manager (CTRL-ALT-DEL) and go to the "Processes" tab; check to make sure that there aren't any background programs sucking up memory (if a program is taking up, say, more than 50,000 K of memory, it'll be slowing down TB)