I have used the same Win 7 install disc on several computers, always have to have a valid registration number for each though, I bought one from Arhive and several weeks later it turned out to have been an MSDN number and MS kicked it out. Arhive did send me a new one at no charge and so far so good.
I have to reinstall my win7 on account of a virus that took out explorer.exe... sysrestore, dskchk, and nothing would work. (I am able to backup my documents though, thank goodness) and I tried calling microsoft to ask but they're currently closed.
my question is though: I downloaded win 7 from microsoft and burned it to a dvd that doesn't seem to be working, even though there are no apparent scratches or anything, but still have the serial number. I DO have legitimate win 7 disks that I can use to install a fresh copy, but both disks have been used on other computers in my house
Will I be able to reinstall win7 and use the serial number for my computer, or am I supposed to deactivate it somehow?

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic