when i try to install it says that i already have fallout 3 installed but i deleted it a long time ago and i deleted save files,mods and its not in panel

HELP

First of all welcome to the forum.

Likely Fallout 3 has some files in the registry and they were not removed.

Are you able to repair the installation in add/remove programs.

If not you can use CCleaner to clean the registry. http://www.piriform.com/ccleaner/download