trying to reinstall cod4

I've had cod4 installed on my computer. I've uninstalled it. Now I've been trying to intall again but when I put the disc in a menu comes up as if it was already installed. I can click play mp for example but it doesnt work. I tried to uninstall but it doesnt work. any ideas on how to fix this?

Start menu<my computer<add/remove programs, try to find it in there, and uninstall it.

If this doesn't work PM me I have more possible fixes.