Why don´t you just scan your computer with an up to date AV scanner ? there are plenty out there and if you don´t want to set up a new OS, i think this is the best option. If the scanner finds nothing, you should consider letting your PC off for a week than (ofc via another PC) download the new AV database, which the AV uses to detect maleware, and scan again, if this is a more populat maleware and not something specifically crafted for you by your nice friend, ith should find it.
Yes I've updated my AV software but when I scan, there are nothing. Maybe Avast Anti Virus that I used I not strong enough. So I have to use another program that recommended on the internet which can strongly kill malware like what I have. And its worked, so maybe I have to be more careful when deciding download any program on the internet especially bitcoin related. Thank you for your advice, I will try when I meet them again (yeah, of course, I hate to meet them in any condition).