Re-installing Win7 OEM on Virtual Machine?

I really don't know the answer to your question but I will try to find someone who can.

It's certainly not recommended to use OEM licenses in VM's - but it is a supported scenario.
Yes, you can reinstall the license into a new VM - but it may complain if the new VM is either in a different host, or different VM manufacturer. (it depends on seeing the same 'hardware' in the new install as in the old).
My recommendation would be to back up the file created (vhd, etc) to external media, so you can just swap it back in at need.

NoelDP said:

My recommendation would be to back up the file created (vhd, etc) to external media, so you can just swap it back in at need.

Are you suggesting a system image restore to a VM. Aren't you presented with the same licensing question if the VM is different ?

In most VM scenarios, the guest machine is held as a single file on the host - with a limited number of auxiliary files for the settings, etc.
Copying those files enables the guest to be recovered from the backup - simply by swapping the copies back in place of the corrupted files.
It's not a question of a 'restore' as such - simply a file-copy operation. I always keep two copies of the original install - one before activation (so I can work on an unactivated/non-genuine system if necessary) and one that's been activated after update to whatever the current/required status at install time was - this enables me if necessary to get back to whatever state I need to very quickly. Tis works in both VPC and VBox - but I've never tried VMware.

MJF on VMWare, I always install to a newly created folder. You can simply copy that folder as a backup. If you get corrupted files, delete your current folder and paste the backup folder in place of the original. No new activation is required.

paulf22 looks like you have all kinds of help.