Microsoft have now released some free and very good security software for your licensed version of windows. This includes anti-virus / anti-malware and SteadyState for shared access computers.

Firstly lets look at Microsoft Security Essentials:

Microsoft Security Essentials provides real-time protection for your home PC that guards against viruses, spyware, and other malicious software.

Microsoft Security Essentials is a free download from Microsoft that is simple to install, easy to use, and always kept up to date so you can be assured your PC is protected by the latest technology. It’s easy to tell if your PC is secure — when you’re green, you’re good. It’s that simple.

Microsoft Security Essentials runs quietly and efficiently in the background so that you are free to use your Windows-based PC the way you want—without interruptions or long computer wait times.

Download here

Secondly lets look at Microsoft SteadyState

Windows SteadyState is a tool developed by Microsoft that gives administrators enhanced options for configuring shared computers, such as hard drive protection and advanced user management.

It is primarily designed for use on computers shared by multiple people, such as internet cafes, schools, libraries etc.

SteadyState is the successor to the Shared Computer Toolkit. SteadyState is available free of charge from Microsoft for computers running Windows XP and Vista. A 64-bit version is not currently available.

Download here