Yesssss!!!

After months of not being able to play this game due to a lost Steam account I checked on to this forum. Low and behold, there on my profile is my Steam account name. I quickly get my list of passwords up and frantically search through. One of them works. I am now logged on the Steam account that I registered N:TW on.

Quick question, I registered the CD key with this account but I threw away the manual ages ago. Will I still be able to install?

Yes.