Add an exe as File Explorer preview handler

It's possible that the NumThumbnails registry value is set to 1. What it does is if you open more than one instance of the program, it stacks the items instead of showing the thumb images.

Start Regedit.exe and go to the following registry key:

HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Taskband

Delete the NumThumbnails value

Exit Regedit.exe, logoff and login back.

(via Increase Taskbar Thumbnail Preview Size in Windows 7, 8 and 10)

Follow these directions to edit the Registry and assign the Windows Text Preview Handler to the .js file extension. (Based on this How To Geek article.)

1. Open Registry Editor
2. Navigate to HKEY_CLASSES_ROOT\.js and make note of the content of the (Default) value. This is the ProgID to which the .js extension is registered:
3. Navigate to the ProgID's key. We'll find our key at HKEY_CLASSES_ROOT\JSFile
4. Expand the key. If necessary, create a subkey named ShellEx
5. Under the ShellEx key, create a new key named {8895b1c6-b41f-4c1c-a562-0d564250836f}. Note: According to MSDN the presence of this exact value tells Windows that this is a preview handler.
6. Select this newly created key and set its (Default) value to {1531d583-8375-4d3f-b5fb-d23bbd169f22}. This is the ID for Windows' Text Preview Handler.
7. The change will take effect immediately.