Segundo o site da Microsoft, isso é possível
The ProgramFilesDir registry value is located in the following registry subkey: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion You may want to use the ProgramFilesDir registry entry to change the location of the Program Files folder. Additionally, you may want to modify every reference in the registry to point to the new Program Files folder. You may also want to move the contents of the original Program Files folder to the new location. However, we do not test changes to the default location of the Program Files folder. Therefore, we do not recommend or support modifying the ProgramFilesDir registry value to change the default location of the Program Files folder.
Mas, de acordo com eles, também não é recomendado
Microsoft does not support changing the location of the Program Files folder by modifying the ProgramFilesDir registry value. If you change the location of the Program Files folder, you may experience problems with some Microsoft programs or with some software updates.