CD Key lost

Hi everyone! This is the first time I'm posting in these forums =)
Here is my problem. My friend lost his CD and CD key, but still knows his account & password. Can he use my CD and CD key to install the game on his computer and use his own account without any problems or will that conflict with me playing at the same time? I forgot if the account and CD key were keyed together...
Thanks in advance ^^

as far as i know you only need account info.

Can also just download the client from guildwars.com and it will install everything. Takes a lot longer to install but it works.

Great! Thank you for fast answers guys ^^

Edit: Thanks to Berek too =)

Yah, it's not like D2 where the CD-Key is for the game..it's for the account. Your CD Key = Your account. You don't need a CD-Key to install, just to create an account

Just a correction here: you can create an account without a key (but it's pointless), and it's only once you've created the account that you can register the key (which has nothing to do with the CD; the CD is just a convenience for you and you can download the whole content of GW using the client available here: http://www.guildwars.com/support/downloadclient/). Once registered to this account, the key is no longer usable and gives you access to the corresponding GW campaign.

Hope this helps!