portable antivirus
Kaspersky Virus Removal Tool
Kaspersky Virus Removal Tool is a free stand alone antivirus toolkit. Although it does not provide real time protection from viruses and can not stop a threat from entering your system, it can be used scan for, disinfect, and remove existing viruses or infections that may currently reside on your PC.
HiJackFree Malware Scanner
a-squared HiJackFree, now called "Emergency Kit" is a Malware Scanner and informative system analysis tool that advanced users and administrators can use to help detect and then remove all types of Malware; HiJackers, Spyware, Adware, Trojans and Worms. It can be used to manage autoruns, processes and associated modules, control Browser Plugins, and view all DNS entries.
Sophos Anti-Rootkit - Removal Tool
Sophos Anti-Rootkit is a portable tool that can be used to discover and remove any rootkit that may reside in a computers running processes, registry or on a local hard drive. A rootkit also known as (Root Kit) is basically a set of tools that are used to conceal a malicious program from the computer user.