Cmon dude, in most cases whatever the malware is, it's going to put something at HKCU/HKLM\Software\Microsoft\Windows\CurrentVersion\Run - remove anything out of the ordinary.
Not to mention if there is a rogue process they aren't difficult to see in task manager, end the process, from there you can search for it and delete it, restart your PC, rinse and repeat.
This is a brief overview but it clears out a vast majority of malware.
There are dozens of symptoms you could experience if a virus left something else on your PC: pop ups, slowness, security apps don't work, pages are redirected, error reporting is disabled, automatic updates are disabled, etc.
There are other tools like a firewall and router that can help keep your PC secure an anti-virus program is not an all in one solution.