Vista Serial on Mac not working?

[Tragedies]

I installed a legit copy of Vista a while back on my Mac, and it said I should enter my serial key with in the 30 days. I did so, it said activated but for some reason about five days later it said I needed the key again. I did this again, worked and once again after five days it said please insert a key. Can anyone tell me whats wrong?

 

[Mac-Addict]

Was the key an OEM version? If yes was it ever registered with another machine?

 

[Tragedies]

Whats OEM? And yes, it was registred on one other computer in the house.

 

[M@lew]

You can only use a serial on 1 computer. It won't let you do it on any other.

 

[dukebound85]

Whats OEM? And yes, it was registred on one other computer in the house.

there is a reason for serial numbers haha