Update: - found a simpler method using the registry

Add the following entries to the registry or download the file here
REGEDIT4

[HKEY_CLASSES_ROOT\Folder\shell\ListToClipboard]
@="List Files To Clipboard"

[HKEY_CLASSES_ROOT\Folder\shell\ListToClipboard\command]
@="cmd.exe /C dir \"%l\" /b | clip"

The small utility lists all files and folders to the clipbaord

ListToClipboard.exe

Syntax:
ListToClipboard.exe C:\Program Files

Example:
C:\Temp\ListToClipboard.exe C:\Program Files

Alteratively you can add it to the right context menu with the following registry key
Right clicking on a folder and choosing "List Files to Clipboard" will list all the files within that folder to the clipboard.
Note that ListToClipboard.exe is copied to C:\

Licence/Copyright: no restrictions at all.

Visitors:

For those that are interested ...
Written in VB6, Standard exe with all forms removed and one module added.

Public Sub Main()
    Dim cmd As String
    Dim filename As String
    Dim clip As String
    clip = ""
    cmd = Command()
    If Right$(cmd, 1) <> "\" Then cmd = cmd + "\"
    filename = Dir(cmd, vbNormal + vbDirectory + vbHidden)
    While filename <> ""
        clip = clip + filename + vbCrLf
        filename = Dir
    Wend
    Clipboard.Clear
    Clipboard.SetText clip, vbCFText
End Sub