mariv I wanted to post that it does work so peeps will know. We can look at your issue if you want.
Original ndis.sys from Windows 7.7000 is 700,680 bytes and dated 12/13/2008, 0200AM.
You might also find it in c:\windows\winsxs\x86_microsoft-windows-ndis_31bf3856ad364e35_6.1.7000.0_none_183111f35806a1f8.
WinSXS is the 'real' location of each file in c:\windows; a driver
could replace the file in c:\windows\system32\drivers
but it would not be able to change the one in winsxs.
dir /s ndis.sys