Ulteo Virtual Desktop is free.
A full Linux system that integrates nicely into Windows

You save time because you can have both Windows and Linux applications integrated into a single desktop. Additionally, the Ulteo Virtual Desktop is a safe and virus-free place. It will even self-upgrade regularly with latest version of the system and its applications.

It's been designed for individuals and corporate users who need to use both Linux and Windows applications within the same desktop environement. A full range of Linux applications are supported in the standard vers

From the Ulteo "My Digital Life" panel, you can add new "application balls", such as additional desktop application, games and soon development applications! It's very easy to add or remove and always leave a clean system.

• Requires a PC (x86-based) with a modern 32-bit CPU and at least 512MB RAM.
• At least 4 GB of free HD space is required.
• A PDF reader is needed.
• For a better experience, we recommend a DualCore CPU and 1GB RAM.

Ulteo also includes automatic system and application updates as well as document synchronisation across all Ulteo systems. Applications can naturally access the user’s documents in the My Documents folder and sound and printing are also supported on the fly.

Tested on Windows XP and Windows Vista (32-bit only for now).

More info and downloads: Ulteo Virtual Desktop