Blender ships with a subset of Python, but can use the whole Python suite if it finds it installed. This is just a harmless message to inform you that it didn’t find a full Python install it can use on your system and it is using the built in subset.
As far as I know, all Python scripts that come with Blender will run with the built in Python.
There may be external Python scripts which you might download and run manually that might need a full Python install, so in that case you would have to install it. As the message says, you would need Python version 2.6.2 (I believe any 2.6.x should work). I don’t know about Win7, I’m on Linux, but I think if you use a 64Bit Blender, you also would need a 64Bit Python, or both need to be 32Bit. Somebody else who knows more about Win7 hopefully will chip in if I’m telling nonsense :).
EDIT: Oh! I just saw you already have Python, and a 32Bit Blender. So, might that be because the bitness of Blender and Python don’t match? If they match, I’ve no Idea what’s wrong.