fonts can be installed from their location, even if it is not within windows fonts folder.
the easiest way would be to check what the registry entry for that font says.
Try this with extreme caution, do not delete or modify enything:
1. Start -> Run...
2. Type in "regedt32" and hit Enter
3. Navigate to HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Fonts
4. On that list find the desired installed font and see what the path or filename for that font.
5 If it is just a file name it is in the windows/fonts folder, if it is a path then that is where you should look for it.
Hope this helps

Alex, Abstract Fonts