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:
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.