In WinHTTrack, when Window -> Hide, it minimizes to system tray. When something
happens to explorer.exe, like it restarts, and when WinHTTrack was minimized
to tray before explorer.exe's crash, then WinHTTrack's tray icon will not
reappear anymore - have to kill WinHTTrack's process and restart the project
all over again.
And yes, WinHTTracks tray icon is the only tray icon which doesn't reappear.