The ability to downgrade Windows 7 to a previous version has been a hot topic these last few days and can be quite confusing, so I thought I’d put a post together to help make it clear what the rules will be 🙂
Windows 7 Pro & Windows 7 Ultimate OEM licences will be able to downgrade to Vista for an unlimited amount of time.
Windows 7 Pro & Windows 7 Ultimate OEM licences will be able to downgrade to XP Pro for 18 months only or until a Service Pack is released, whichever is first.
Q: What is an OEM licence?
A: OEM stands for “Original Equipment Manufacturer” and these are licences that come pre-installed on PCs when you buy them from PC World, Dixon’s etc.
Q: What about OEM licences of Windows 7 Home or Starter?
A: The OEM EULAs of these version do not permit downgrade rights.
Q: What if I purchase Windows 7 through Volume Licensing?
A: The versions of Windows 7 available through Volume Licensing (Open, Open Value, Schools, Select, EA ) will contine to have full downgrade rights to any previous version without time restrictions.
There are lots of people saying lots of things about this but I don’t really see it as being too much of an issue. In a nutshell, Microsoft are saying that after June 2011 the majority of home users won’t be able to downgrade a new PC to an OS that is 9 years old.
When you really think about it-who will want to? In 2 years-will there really be any reason for people to be using XP? I don’t think so. The applications that won’t work on Windows 7 will have been replaced with new, Windows 7 compatible versions and all will be good 🙂
Cloudy with a chance of Licensing 
Yeah, it’s good to see that there are still some people tht look at this from a sane perspective.
One thing you didn’t mention are small companies that don’t have SA on their Windows licenses. However, these smaller companies can usually upgrade to Vista easily – my primary job is dealing with Small Businesses, and upgrading them to Vista is easy – there are usually one or two business specific apps that need to be looked at, but most software vendors have moved to support Vista.
Another thing that was mentioned were appliances like point of sales systems that are currently based on Windows XP. For those, there’s Windows embedded licensing (you can license Windows XP Professional using embedded licensing), or custom tailed XP Editions like POSReady 2009.