I have the Star Trek Online disk but when i try to install it it wants the key, when i input the key it says its allready being used.
i then tried to download the client but at 96K it would have taken forever to download.
Sorry to but in but I think I can answer the OP question as I just had to re-install windows on my sons computer, so instead of downloading the client again for STO, I used my CD to install the game for him.
When I installed the game, a web page automatically poped up asking for the key. I just closed the window and the install continued as it was still running in the background. Since my sons key is already attached to his account, it did not matter that I did not enter it again.
Whoever setup the install should not have created this pop up to ask for the key, it would probably have been better to give the option to go to the STO website and enter the key with a notice that if you have already done this, you do not need to do it again.
So in effect, you can install the game on as many pc's as you want, but you can only have you account 'in game' on one at a time.
Hope this helps, and if I am wrong I am sure someone will tell me