Anonymous .. "for the time being"
IF the infected files were moved into quarantine, and IF the system has been running normally while in quarantine, there should be no problem removing Spybot.
Since your friend has been without protection, I would suggest also scanning with Malwarebytes' Anti-Malware, to be on the safe side. It's free and can be downloaded from here.
I'm surprised to see Trend and Spybot still haven't worked out their "issues". See "Trend Micro brands Spybot "incompatible". The article is 2 years old. This 4 page thread at the Spybot Forum is 5 years old! If you wish to keep Spybot, the first article offers a workaround. FWIW.
Best of luck..
Working on a friends computer that was unprotected. Got virus's and they wouldn't let him load his Trend Micro that he had for his other system. Virus kept preventing it from loading. Fianlly got Spybot S & D on system and cleaned it. Now Trend Micro is saying I have to remove Spybot to load Trend Micro. If I remove Spybot, what will happen to virus's it has captured?