office 2013 kms server

[sted]

im trying to add office 2013 to my existing kms server setup (server 2012 NOT r2) but when I run the tool from ms I get so far in then get this message if I enter the key clicking next without entering a key (to see if it appears later dosent help)

 

im sure ive installed this before but I think always on 08r2 or win7/8.1 boxes but I don't want to risk killing my windows/office 2010 kms server settings as atm its running fine and I haven't got any 2013 clients just trying to plan ahead as I prefer 2013 if for no other reason than using lync for remote support

 

any ideas as aparantly with this my googlefu is weak