Hello,
You can install different versions of TDP on the same computer. For example you can have 4.0.1 and 4.1 installed on the same machine.
But unfortunately you cannot install 32-bit and 64-bit TDP with the same version on the same computer.
So if you have 32-bit version of 4.0.1 installed and you try to install 64-bit version of 4.0.1, the installer will ask you to uninstall the 32-bit version first.
Libor