I've been updating the computers here at the office and installing AVG Free Anti-virus on the computers that only had expired Norton software. I recommend this software highly. The virus database is updated constantly and it's free to get the program and always free to download the updates. Grisoft, the company who provides this service, deserves recognition for doing something to make the net safer (compare to Microsoft, which habitually releases vulnerable programs). So use AVG Free, and when you do want to buy some software, keep Grisoft in mind.