Window 7 Update v. Windows 7

This might be a big "duh," but I need to know for certain, and it isn't covered anywhere (at least anywhere I can locate).

I bought a machine some time ago with the Windows 7 Update disc from Vista.
Ok. Now I have a notebook that came with Windows 7. They are both Dell machines. I notice that with the same amount of RAM and the same processor in both machines, the one that came with Win7 preinstalled runs much better than the ungraded one.

a.) can I use the Windows 7 disc to wipe and reinstall on the machine that was just updated? Both reinstall discs are Dell disks.

b.) since they are both machines from the same manufacturer running the same operating system, is it ethical/legal to do so...? Both reinstall discs are Dell disks.

 

Answered http://windows.microsoft.com/en-US/windows7/Activating-Windows-7-frequently-asked-questions