The preinstalled Microsoft Windows Operating System and preinstalled Microsoft Office supplied with your Dell system typically falls under an OEM license.
OEM stands for Original Equipment Manufacturer and in the case of a Dell computer, the OEM is Dell and the software is tied to that particular computer via the service tag on the motherboard.
• Therefore you cannot transfer it from an old computer to a new computer.
• You cannot legally use a Dell Windows 7 OEM disc to upgrade an older computer running Windows Vista or Windows XP to Windows 7 or likewise from Windows XP to Windows Vista unless an appropriate license is purchased.
• You cannot legally downgrade a Windows 7 Home Premium/Windows Vista Home Premium system to Windows XP.
There are some cases in which you may legally downgrade to an earlier version of windows. These are typically included in the Ultimate and Professional/Business version of 7/Vista. See here:
For Windows 7 Professional and Windows 7 Ultimate, one may use downgrade rights. This gives one the ability to install Windows Vista Business edition or Windows Vista Ultimate Respectively. One may also downgrade to Windows XP Professional (see chart).
Note there are no downgrade rights available for Windows 7 Home Premium or Windows 7 Starter. Note Windows 7 Ultimate and Windows 7 professional include a feature called XP Mode. This was designed to give one the chance to run applications that weren't yet ready for Windows Vista/7.
For Windows Vista Business and Ultimate Edition one may downgrade to Windows XP Professional (see chart).
Note there are no downgrade rights for Window Vista Home Premium and Windows Vista Home Basic.
If you have the correct installation media from an old system, you may use it to install Windows XP Professional on a system that came with a Windows 7 Professional or Ultimate License. It should automatically unlock if installed via the Dell BIOs. If you don't have the media and wish to perform downgrade rights you will need to contact Dell.
In the case of downgrading to an older OS you will need to check the system has the required drivers, present for the older OS you are planning to install. If available they will be on the Dell Drivers and Downloads Page.
Since Windows 7 64 bit which is very stable has became the default system, it is getting harder and harder to find the drivers for the likes of Windows XP. If you cannot find some ask on the forum and you might find a workable driver set. Downgrade rights are generally more supported on the business systems such as the latitude and optiplex and not home systems such as the inspiron and dimension.
Upgrading after a Downgrade
You may of course reinstall the original Operating System on your computer after performing the downgrade.
Dr Philip Yip Tech Enthusiast and Author of the Unofficial Dell Windows Reinstallation Guide