Cant delete games!

Hi everyone. Well some time ago i was checking the games i had installed and i deleted some of the ones i didn't play anymore. So now its passed like 3 months and i wanted to install them again, but everytime i inserted the CD, the installation stopped and there was a message that said that the game wasn't uninstalled. So i tried absolutely everything to uninstall them, but nothing seemed to work, it keep saying the game was still there. I also tried deleting them from the control panel but the names dont figure. And all the programs i tried didn't help either. I started researching a bit and it said that i had to delete them from the registry, but i have no idea how to do that. Thanks people for the support, i really need some help on this one.