Q. If my computer already has a virus, are the antivirus software programs that you recommend good, or is there another way to clean it up?—Charles Jeannel, Los Angeles

A. Some computer viruses can limit your ability to properly install and run protection software. If you want to try to eliminate existing bugs, we recommend downloading and running the free Malwarebytes Anti-Malware scanner. If necessary, you can download it on another computer, then transfer over the program using a USB flash drive.

For more on preventing viruses, check our security software buying guide and Ratings and find out how much security software you really need.

Send your questions to ConsumerReports.org/askourexperts.

This article also appeared in the July 2015 issue of Consumer Reports magazine.

More from Consumer Reports:
Best cars for making it to 200,000 miles
6 costly estate planning minefields and how to avoid them
Why you should wait to buy a laptop

Consumer Reports has no relationship with any advertisers on this website. Copyright © 2006-2015 Consumers Union of U.S.