VMware

The VMware-software emulates a computer so that GNU/Linux or other OSes thinks it has been installed on a real computer. So by ‘toggling’ back and forth you actually switch computers (albeit a simulated one). For a similar solution, you could also install CoLinux or Cooperative Linux that cooperatively lets you run the two operating systems side by side. 

• http://www.youtube.com/watch?v=Bh5H2KMX6Ek
• Cooperative Linux
• VMware
• HOW TO: Run Other OSes On Your PC
• How to Install Ubuntu Linux on Windows XP using VMware Server
• Beginner’s Guide: Run Linux like any other program in Windows
• How to install VMware Player on Windows XP
• Run Ubuntu Linux on Windows XP using VMware Player
• VMware Workstation 6 has been released