I started with Windows 7 and I realized that I couldn't drop files on .js javascript files anymore.  I couldn't even see a highlight when hovering over the target files, like I could it behaved with other files (vbs, jse and bat). "What the hell?", I thought
I have been googling for so long without answers to my problem that I just have to write it here.  Hope it saves someone some time.
A lot of things that I found did clear my path to the solution below, but, for the record, none of these were thé solution:

  1. filetype settings or their association settings
  2. "open with" settings
  3. registry keys and values in ".js" as "JSFile" in HKEY_CLASSES_ROOT, especially "shell" keys
    1. DropHandler
    2. Open Commands
    3. etc..

As a matter of fact, everything worked with jse files, so I made sure the registry looked exactly the same for ".jse" and "JSEFile" in HKEY_CLASSES_ROOT.  No luck.
Until I found the following "UserChoice" key, but this time in HKEY_CURRENT_USER:

HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts\.jse\UserChoice

So I deleted that key UserChoice and ..Tada..works now