Method 1: Add via Control Panel

Well you can do by selecting 'System' from the Control Panel, selecting the 'Advanced' tab, the 'Environment Variables' button and then finding the PATH (user or system) and editing it in the agonisingly small edit control which doesn't seem to have changed since Windows 3.1. (He says, exaggerating only a little)...

Source: http://groups.google.com/group/comp.lang.python/msg/dea9f45e03406828

Method 2: Add via a Python script

... or, I was going to say, you could run Christian Heimes' win_add2path.py script which is in c:\python26\lib\tools. Except that it wasn't added until python26 and uses _winreg.ExpandEnvironmentStrings which also wasn't added until then. (I think). But for anyone else still watching the show...

Source: http://groups.google.com/group/comp.lang.python/msg/dea9f45e03406828

Method 3: using a small .bat file

Source: http://groups.google.com/group/comp.lang.python/msg/5656baf6e811ccb0

I highly recommend against adding C:\Python25 to your %PATH%. You can get the same effect by adding a simple bat file to C:\Windows\System32

@C:\Python25\python.exe %*

Call it python25.bat and you are done. Apropos call, don't forget to "call python25" in batch files. :)

...

My way doesn't add the dlls to the search path. It allows you to have multiple python commands at once, too. I have shortcuts for python24, python25 and python26 on my Windows box.