Another possibly solution. On Windows XP it adds the following context menu to each folder regardless of its content:
Enqueue in foobar2000
Windows Registry Editor Version 5.00
[HKEY_CLASSES_ROOT\Directory\shell\foobar2000.enqueue]
@="Enqueue in foobar2000"
"LegacyDisable"=""
[HKEY_CLASSES_ROOT\Directory\shell\foobar2000.enqueue\Command]
@="\"C:\\Programme\\foobar2000\\foobar2000.exe\" /add \"%1\""
Play in foobar2000
Windows Registry Editor Version 5.00
[HKEY_CLASSES_ROOT\Directory\shell\foobar2000.play\Command]
@="\"C:\\Programme\\foobar2000\\foobar2000.exe\" \"%1\""
Add to Winamp's Bookmark list
Windows Registry Editor Version 5.00
[HKEY_CLASSES_ROOT\Directory\shell\Winamp.Bookmark\command]
@="\"C:\\Programme\\Winamp\\winamp.exe\" /BOOKMARK \"%1\""
Enqueue in Winamp
Windows Registry Editor Version 5.00
[HKEY_CLASSES_ROOT\Directory\shell\Winamp.Enqueue\command]
@="\"C:\\Programme\\Winamp\\winamp.exe\" /ADD \"%1\""
Play in Winamp
Windows Registry Editor Version 5.00
[HKEY_CLASSES_ROOT\Directory\shell\Winamp.Play\command]
@="\"C:\\Programme\\Winamp\\winamp.exe\" \"%1\""
You can copy the content of the code boxes into a text editor and save it as reg-file. Be aware that at the end of each reg-file there have to be two empty rows.
Try then to import the registry files (you might want to save a system restore point before).
And again: this works on Windows XP, I am unsure how Windows 7 behaves. First you should start the Windows Registry Editor and check whether you have this entry
[HKEY_CLASSES_ROOT\Directory\shell\
and how it looks like. Maybe you have to adjust the path to your program files directory first.