Best antivirus out there. Just install the latest version. Make sure you use at lease windows xp with service pack 3. else this wont work it will continuously stop any attacks and show you the information also.
No need to scan pen drives. it will be done automatically if you insert the pen drive.Buy the total security for high performance. It is best for office and home uses.Even you dont update, the software works good in detecting viruses./
It will remove the active viruses in your computer when installing itself.