Sorry guys, for misleading you in my 1st message, the mentioned registry fix does
work in Windows 7, too.
I had made a mistake earlier by adding the fix "ShowDriveLettersFirst"=dword:00000004 by error manually under HKEY_CURRENT_USER instead of HKEY_LOCAL_MACHINE.
I now deleted the wrong entry from HKEY_CURRENT_USER and made the fix correctly by merging a little .reg file with following contents:
Windows Registry Editor Version 5.00
Copy & paste into Notepad and rename it a .reg file. It works!