I am not sure if you are talking about Microsoft Security Essentials, but if this is the antivirus program causing your problem, then uninstall it. There are many antivirus programs out there the are free such as Avira, AVG, Avast, etc.
You can also delete the antivirus program and NOT run an antivirus program. You can only do this if the program AC's database is on is NOT on a client.
It is not best practices to run AC on a computer used by other users.
