Different python versions confusion under Windows Vista x64

[Edward Diener]

In Windows Vista x64 I have installed python 2.6 64-bit version and 
python 3.1 64-bit version to separate folders. Within the command 
interpreter I add python 2.6 to the PATH.

In the command interpreter, When I type python somescript.py with an

import sys
print (sys.version)

in the script, it shows:

3.1.2 (r312:79149, Mar 20 2010, 22:55:39) [MSC v.1500 64 bit (AMD64)]

In the command interpreter if I type 'python' I see:

Python 2.6.5 (r265:79096, Mar 19 2010, 18:02:59) [MSC v.1500 64 bit 
(AMD64)] on win32

Does anybody have any ideas why this is happening ?