old versions of python worked on old versions of winpe by copying the c:\python25\ directory over to the mounted (iso,usb) filesystem, then rebooting with the media and running the python.exe from the ramdrive. This formula no longer works with 64 bit versions of winpe (which is one way to push win7-64bit. When it's tried one gets platform based errors.
Do you have any log files or screenshots of what exactly happens? I have zero experience with WinPE, so that's an obvious barrier here, but there's also nothing to go by in figuring out where the problem may be.
You need to install the MS CRT (msvcrt90.dll, along with its assembly manifests and stuff) as well; it's not surprising that copying over an installation doesn't work. I'll also point out that this is not a bug: copying over an installation is not supposed to work.