Can you be dishonest and get MS to activate for you? Maybe, but that would be illegal.
Options: Buy another legal license (individual or a family pack with 3 licenses).
What will happen when you use the same key on a second instalation, when you try to activate it it will be deemed an illegal copy and can be blacklisted by Microsoft. The pc with with the original instalation is subject to likewise being deemed illegal. You now finish up with a worthless OS.
Everyone is correct here. You may be able to install, but will not be able to activate and as a result Windows will be deemed non-genuine. It is illegal to do this. Windows 7 comes with one license meaning it can be installed on one computer only. If you wish to install Windows on multiple computers (as upgrades), I recommend the Windows 7 Family Pack that will allow you to install Windows on 3 computers.
Cheers, Cassandra Microsoft Windows Outreach
Ahem, what about a VLK, one key to rule them all, but only for corporate customers.