Emsisoft Free Emergency Kit's can scan and clean malware-infected PCs without having to be installed. Free Emergency Kit runs from USB drives and similar devices which makes it pretty handy for, as the name implies, emergencies. It detects, quarantines, or removes viruses and malware, adware, PUPs and other programs that may be annoying, unwanted, and unnecessary but not a threat.
The Scanner program searches for viruses, Trojans, spyware, adware, worms, dialers, keyloggers among others.
Also included is Commandline Scanner but doesn’t have a GUI and is for professional use; it’s not something most of us will want to mess with. The same with HiJackFree; it helps advanced users to detect and remove Malware manually. BlitzBlank is another tool for experienced users or anybody else who is plagued with Malware on a daily basis. It deletes files, registry entries and drivers at boot time before Windows and all other programs are loaded. Not something computer illiterates will want to mess with.
You begin by running Smart Scan, which ferrets out malware and then run a full scan. The program recommends quarantining any items in the scan results if you're not sure they can be safely deleted. If everything runs OK, you can delete the quarantined files later.
If your computer is packed full of crap the process can take a long time, but normally it’s fast and will often find stuff other software won’t. That said, you should not rely on this software as your only protection.