Intall python 32 bit & 64 bit in different paths
Delete the PYTHONPATH from your Environment Variables
If you need use immunity debugger make a .bat instead:
set PYTHONPATH=C:\Python27\Lib\site-packages;C:\Python27\Lib;C:\Python27\DLLs
start ImmunityDebugger.exe
Attached image with my PATH env.

Intall python 32 bit & 64 bit in different paths
Delete the PYTHONPATH from your Environment Variables
If you need use immunity debugger make a .bat instead:
set PYTHONPATH=C:\Python27\Lib\site-packages;C:\Python27\Lib;C:\Python27\DLLs
start ImmunityDebugger.exe
Attached image with my PATH env.