Never thought you for a "serious thread"
To answer your question, no need deactivate, just install it when you load up Windows 7. If you hit your limit on activations, shoot support an email asking them to reset your activations.
As for installing on 2 machines, it is allowed as the EULA states.
YOU MAY:
1. Install and use one copy of the SOFTWARE on a single computer.
2. Install a second copy of the SOFTWARE on a second computer only if you are the main user of this computer (home computer or laptop for example).