When you install a program, it asks you the path where you would like to install the Program Files, why didn't you use it to browse to the 1TB Drive after creating a new folder?
Most people feel and change the default reg entry like you have done, and, it has been proved to be the most unreliable since the registry entry is only for OS files. All other software companies have there own way/method of installing stuff, and that is why they ask us everytime.
Since you have messed up the registry already, a reinstall of the OS would be a better option. Unless you remember what you changed and could go back and reverse it.