The first thing I do when checking out a friends computer is to run a virus scan on it. To do that I run Windows Defender Offline. You download the software to a CD and then boot from the CD. That way you know the virus hasn’t loaded first. You may have to set your Bios up on your computer to load from the CD first.
There are 2 versions – a 32 bit and a 64 bit. If you have a newer computer I would try the 64 bit version first. Older computers probably need the 32 bit version.
Here’s the link for Windows Defender Offline.
Note – here’s another option doing the same thing with Bit Defender.