Ok a friend and I were having a discussion in which we both have comnflicting answers, so basically Im here to find out which of us is right.

We were talking about WIndows XP and registration keys. My question was if I installed windows XP on lets say my pc, and I dont have a reggistration key, but my friend across teh street has an original copy of xp with product keys, and I called him and ask him for his product key would it work for my XP installation?

Now my friends answer to thiat question was no.

I however said then that would mean every product key is CD specific (meaning the key only works for the CD it came with) to which I say if that was the case then Im sure they Keys would be one use only in which case If I had two PCs I wanted to install that same copy of windows On I couldnt do so on teh secind Pc because I used the key on teh first one, and even then if Keys were CD specific (meaning the only work for the CD they came with) then how would thinks like KEYGENs exist. I mean it would be a 1 in a billion chance than the KEYGEN would generate the correft Key for the CD your using ight?

In short, very short, No.
What you are asking is indeed Illegal. The Windows Key belongs to the PC it came with originally. You will have to purchase another Product Key from Microsoft to be Legal.

well Im not asking whether or not its legal i know that it is, plus I already have windows so this is all hypothetically speaking, the question im asking is whether or not it would actually work, my friennd says it wont and I say it will on the grounds that if something like that didnt work then keygens wouldnt exist because none of them would ever work either.

Whilst this is against the terms of the Windows licence, if you have the same version of the OS then this would work.

For a repair only and not an install.

so then IF i lets say installed my version of windows, but didnt have a cd key so I called the person acoss the street and asked him to ead off his cd key to me, then I input it duing installation yours saying the installation wouldnt complete and I wouldnt be able toio run windows?

If you had a legitimate version of windows you would have the product key too and not require his.