When Windows XP came out a long time ago I purchased a copy, of which I wonderously still have the CD and case. So, I was installing boot camp on my Mac (I liked my wife's so much we went and got one for me
)so I could still play the couple of games I like to play. Boot Camp requires a Windows XP SP2 version of the installation media so that it will find the appropriate partition to install to, so, I used a Windows XP Pro SP2 installation disk that came with one of my other name brand computers just for the installation. I then tried to activate my version of windows using the original activation key from the version I purchased. So, I type in the activation key and am informed it's not a valid activation key. OK, so let's try an activation key from some other computer, it too is listed as being invalid. Now, I'm getting rather frustrated and I try the Telephone option, enter the code presented in the Telephone activation dialog and am informed that I don't have an authentic version of Windows XP and to hold on the line to speak with a tech, so I hold on the line which is promptly hung up with just a busy signal 
So now I'm stuck with what to do next, I have no idea
I guess I'm going to retry installation and hopefully we'll get past it this time, if not guess I'll just do without.