I keep getting a notice that the game can't be installed because the game already exsists. How do I get rid of this problem or the rest of the game that I had?
Uninstall the game (go to control panel,add/remove programs).If any files are left in your CoH installation folder,delete them all.Also try uninstalling the mods,if you have any.
In addition to that, you most likely need to clean the system Registry too.
Go to Start → Run, type RegEdit and click OK to open the Registry Editor. Now, look under HKEY_CURRENT_USER → Software and HKEY_LOCAL_MACHINE → SOFTWARE. Look for CoH related folders and entries. They're most likely listed under the name of the game itself or the name of the developer / publisher. Find and delete all related folders and entries, but be extremely careful not to delete anything else by accident. One wrong move can screw up your operating system beyond repair. Blame Microsoft for making it so sensitive. =p
Anyway, when you're done cleaning the Registry, close the editor, reboot your computer and try installing the game again.