Antivirus8 2010!

Somehow my daughter's pc was infected by Antivirus 8 yesterday - 10/20/2010 (perhaps a current version!)  - it is running an updated Norton AV!

At any rate, Norton was disabled.  We found a removal tool that this virus did not know about and removed it.  The problem now is that Norton AV will not run due to the virus disabling it.  the question is how to bring back Norton AV - uninstall and reinstall?

appreciate any insights and experiences.