I have an MSDN version of Windows 7 Enterprise.
I think I saw somewhere that this version can be installed on multiple computers with the same serial number. Is that correct? How many times can I use it?
MSDN licensing is a tricky model. Each MSDN license is for a single person, and that single person can install the software on as many machines as needed for development purposes. If you perform any non-development actions on computers with MSDN licenses, you are violating the terms of the license agreement.
Quote from Microsoft:
Many MSDN subscribers use a computer for mixed use—both design, development, testing, and demonstration of your programs (the use allowed under the MSDN subscription license) and some other use. Using the software in any other way, such as for doing email, playing games, or editing a document is another use and is not covered by the MSDN subscription license.
While there is no technical limitation preventing from using an MSDN license as a retail copy, doing so can get you into trouble with microsoft. MSDN licenses are for testing labs to allow a software developer to cheaply test their programs on a wide array of hardware.
If you are not a software developer, then you should not use this license. If you are, then you should read the terms of the license agreement when you purchase this license.
Windows 7 Enterprise is only sold using volume licensing. Therefore, every Windows 7 Enterprise product key is a volume license key.
The number of installations you may use is determined by how many licenses you purchase.