Can I downgrade my copy of Windows?
From CybertronPC Support
Q. Can I downgrade my copy of Windows?
A. The short answer is that yes, most versions of Windows can be downgraded without having to purchase a separate license. Below, you will find a table showing some of the basics of which versions of Windows can be downgraded, and which versions they may be downgraded to.
NOTE : Windows 7 can only be downgraded to Windows XP until April 1, 2011 - approximately 18 months after the release of 7, or until the first service pack is rolled out for Windows 7.
Q. How do I get a downgrade COA?
A. You may contact Microsoft calling their activation line. More information is available here (though the information listed from the link is for Server 2008, it still applies to Windows 7).
Downgrade Chart
| Purchased Operating system | Can be downgraded to |
| Windows 7 Ultimate |
Vista Ultimate XP Pro |
| Windows 7 Professional |
Vista Business XP Pro |
| Server 2008 Standard |
Server 2003 Standard |
| Server 2008 Small Business Server |
Server 2003 Small Business Server |
