vmware-fusion: How Clones affects Windows Licenses

Question

I am considering an upgrade to vmware-fusion 6.

I would like to do the following:

1. Install windows 7 as a Fusion VM, call it base, and leave it alone.
2. Create a clone of base and install IE 7
3. Create a clone of base and install IE 8
4. Create a clone of base and install IE 9
5. Proceed with testing such that I never run base or any of the clones at the same time.

As long as I never run the machines at the same time I do not think I am violating any of MS license agreements. It is no different than if I took a backup of the machine and restored it.

Will I need more than one Windows 7 license to do this?

Would switching to parallels or virtualbox be a solution?

I have sw other than IE that I want to do this with, so I am looking for a generic solution, not one specific to IE.

I am using "clone" as a generic term. If there are ways to accomplish what I am asking such as using linked clones or copying files on the harddrive, then I am open to those solutions as well.