[Tutor] python: can't open file 'test.py' : [Errno 2] No such file or directory

[Pierre Dagenais]

The file test.py is in I:\Python25\MyCode,
if I enter:

   C:\>Python25\MyCode\python25 test.py at the DOS prompt, everything 
works as I would expect.

However when I enter the same command from any other directory I get 
this error:

   C:\>python test.py
    python: can't open file 'test.py' : [Errno 2] No such file or directory

I've set the environment variable pythonpath as
   C:\>set pythonpath = C:\\Python25\\MyCode
what am I doing wrong,
Thank u for your help,