Nasty trojan seems to be gone. Had to do a restore from 10 days ago as earlier tries didn't get rid of it. Antivirus doesn't see it now, but detected it initially. It was Alureon.A
EDIT: Spoke too soon. It showed up again after a second reboot when I noticed CPU and memory usage higher than usual. It builds something using winrscmde, which I understood to be some sort of spooler activity, but I have no printer.