If I suspect a virus the first thing I do is boot into safe mode and then scan with one of these.

1. ESET Online Scanner

2. https://www.clamwin.com/- the portable version is super handy on a system that won't let you search the web.

Followed by one of these in safe mode.
1. Malwarebytes
2. Super Antispyware

Once you have cleaned the virus, use a good antivirus and pay for it. I wouldn't trust a free version on a system I REALLY needed. This is one of the best I've used. https://www.eset.com/us/