If the mouse cursor jitters, or jumps around, then please try manually installing the latest version of ScummVM. Download it from:
After that install ScummVM to the game's installation folder\SCUMMVM (by default either C:\Program Files (x86)\Galaxy\Games\The 7th Guest\SCUMMVM or C:\GOG Games\.
If you are encountering issues with the movie transitions, then please go back to the game installation folder. Once in there find t7g.ini and open it using Notepad. Here find the [t7g] section, and at the end of the commands list in this section, please manually add this one:
Save and close the file.