While Microsoft keeps track of activations, if you have only used your serial one time and it's been a few months, just install using that serial number. If activation tells you that you can't, just call Microsoft and tell them the other computer died and you are switching the activation to this one.
It isn't a big deal this way - and you will always get updates and don't have to worry about being blacklisted.
It doesn't matter how long you use a key for, each time you search for updates or download one, you have to verify your key is legit. They store only 1 hash for the key, so if you install it on computer a) then computer
(and call up and get them to activate for computer
) computer a) will stop working the instant it checks for updates or you try to download a security update from MS because it uses a different hash to computer
I could be wrong and it actually checks your key and computer hash online during Windows startup and not during windows update etc.
Edited by Franpa, 19 January 2009 - 02:59 PM.