Dr.Web CureIt is a free anti software,you can download it and press start to scan your pc,not like common anti software ,you no need to install it ,

just download it and press start to play a scan,you can choose Full Scan” or “Custom Scan,



Dr. Web CureIt: have not built-in update interface.so you need to download last version to keep updated.

Features

Dr.Web CureI:http://www.freedrweb.com/ 
Free#
no need to install it
Don't support the Email, files or web real-time monitoring
not built-in update interface

FREE anti software have many on Internet ,but not any will be functional,i think Dr. Web CureIt is a good idea ,because without any installation you can check your system at anytime you need, you can Cooperate with other anti software to get a fresh system .Like avast! antivirus,
Avira AntiVir Personal Free Antivirus