As a techie by trade, I get a lot of calls from friends and family about computers that start out with "Help!" Often the computer problem can be traced back to a virus or spyware that's managed to get itself installed on the computer. If you're asked to troubleshoot a computer and you think a virus or spyware might be installed on it, download Malwarebytes' Anti-Malware. Malwarebytes' Anti-Malware is a virus and spyware scanner that when installed on your computer can find and remove viruses and spyware that have infected the computer.
While there are many programs out there that provide the same features as Malwarebytes, in my experience here at the library, none of them work as well as Malwarebytes. I've never met a virus or spyware that it couldn't wipe out. It sometimes takes more than one scan and reboot of the computer to completely clear out the offending files but Malwarebytes eventually does the job. Malwarebytes offers two versions of the program, a free version that provides on-demand scanning and a paid version that also provides real-time scanning. You can pay for the additional protection of real-time scanning but for me, the on-demand scanning is sufficient.