|It might be a long shot but try rebooting into safe mode (Press F8 before the windows logo on booutp is shown) and perform a scan then. You should also be able to delete the files then.|
Safe mode is a special mode windows can run, where nothing but essential services are run. This should stop the malware/viruses from running.
I would also recommend performing a disk check on the drives (right click on the drive in "My Computer/Computer" and select properties. Go to tools, and select "Check Now". This should help fix any corruption that the virus/malware has performed.
WARNING Please backup all data from that machine, if things take a turn for the worst you might not be able to recover it. Copy the data to another disk drive before performing any of these steps