Some free antivirus programs include: NOD32 and Kaspersky. The cheapest antivirus programs are the free ones but the protection may not be as great as the paid versions. Some free antivirus programs include: Avast Free, AVG Free, Avira, Bitdefender, Comodo, Immunet, Kingsoft, Microsoft Security Essentials and Panda Cloud Antivirus.

Antivirus software is a necessity with regards to computing. Free trials are a great way of testing various types of antivirus without committing to a long term paid version. Free trials are available from AVG, Mcafee or Norton.

Some viruses are able to turn protection off. Use another antivirus program to check your computer. If you are sure that everything ok try to uninstall the antivirus and install again. If it didn't help call support if you paid for antivirus. Or it the antivirus is free pick another one.

AVG is a reputable free anti-virus program. It has paid options, but basic protection is no cost.

The Trend Micro Online is an antivirus scan that can be found at Free Antivirus, House call Trend Micro, and Antivirus UK websites. All the aforementioned options are free however there is a paid version at Trend Micro's website.