MiKTex local bibtex style

You did not mention where your custom .bst file was located. You could technically put it with the other .bst files in the MiKTeX installation directory, and be able to use it provided you "refresh the file name database":

Run MiKTeX Options (Admin)> General > Refresh FNDB

But the better way to do it would be to save the custom style in a separate folder (preferably in the current 'User' path), then 'register' this location with MiKTeX:

1.Create a folder structure at your preferred location: ..latex/tex/latex/
2.Copy your custom file here (you can save all future custom latex files here)
3.MiKTeX Options (Admin) > Roots > Add > add above root latex folder (../latex/)
4.MiKTeX Options (Admin) > General > Refresh FNDB

Now you can use your custom file. Everytime you save a new custom file here, just remember to "Refresh FNDB".

src: http://latex-community.org/forum/viewtopic.php?f=50&t=21039

Tree:

src: http://docs.miktex.org/manual/localadditions.html