Same problem with me on my 64 bit Windows Vista computer.
echo %PATH% returns:
C:\Users\XXXX>echo %PATH%
C:\Windows\system32;C:\Windows;C:\Windows\System32\Wbem;C:\Program Files (x86)\A
TI Technologies\ATI.ACE\Core-Static;C:\Program Files (x86)\Common Files\Roxio Sh
ared\DLLShared\;C:\Program Files (x86)\Common Files\Roxio Shared\10.0\DLLShared\
;C:\Program Files (x86)\Common Files\DivX Shared\;c:\Program Files (x86)\Microso
ft SQL Server\90\Tools\binn\;C:\Program Files (x86)\QuickTime\QTSystem\;C:\Progr
am Files (x86)\Git\cmd
I installed both Git and GitExtensions in C:\Program Files (x86) and my Build (cmake), TDB, and TrinityCore folders in C:\ in their own folders. I installed Git like you stated above, so any idea what I'm doing wrong?