Several software solutions exist for administrators who wish to protect their computers. The software packages usually work by restoring a computer back to a predetermined configuration after a computer restart.
Steady State is a free application from Microsoft. It works nicely on Windows XP (32-bit) and Windows Vista. It was discontinued in 2010. It does not support Windows XP (64-bit) or Windows 7. If you are using Windows XP (32-bit), this is a good solution. At our Internet cafe we use Steady State to ensure virus-free and stable operation. Download Steady State.
For those using Windows 7 or 8, Microsoft has published a document that describes how to replicate most of the Steady State functionality without the need for additional software. Download the document.
Deep Freeze by Faronics is the most popular commercial product (i.e., not free) for protecting computers. It works on Windows XP/Vista/7/8 (32 & 64 bit).