internet security 2012 cd will not load up

i have 2 computers which have norton 360 but are expiring in a few days so  i have bought norton internet security 2012. On the first computer  i have uninstalled the norton 360 2011 and put the 2012 cd in the computer but it will not load up, i tried the 2012 cd on my other computer and it does load up so why does it not load up on the 1st computer?  was i wrong to uninstall the old norton before i started to unistall the new norton?