First download quicktime 4.0 from this exact website:
http://www.oldversion.com/windows/download/quicktime-4-0

DO NOT use any other version. If you have another version installed, do a full, clean, uninstall of it. And don't download it from anywhere else. Some versions are simply incompatible, like another I tried. Make sure you do a full install of it, and use all of the default options.

Once quicktime 4.0 is installed properly, find the executable in the septerra core directory (should be under C:/gog games or wherever you decided to install it)

Right click it, and use these exact options:

- Check the box beside "Run this program in compatibility mode for: Windows XP (Service Pack 3)
- Check the box beside "Run in 640 x 480 screen resolution
- Check the box beside "Disable display scaling on high DPI settings

DO NOT check any of the other boxes.

Now, REMOVE or DELETE both the ddraw.dll and quicktime files, also located in the Septerra Core directory.

Hopefully it should work 100% on Windows 8.1 now.

It won't have some of the features of the timeslip patch, but otherwise it should work fine now, playing the movies AND not halting the framerate to slower-than-turtle speed.

I hope this helps!

Can confirm this fixing framerate, but movies don't play for me at all.
*edit* Downloaded movies in DB format from another thread here(since the ones in my directory had 0MB), and now works like a charm.

That seems to be my problem I follower the OP and now all works except for no movies.

which tread did you find the DB in ?

::EDIT::
I found a topic that had the Mega link for the DB :D

https://www.gog.com/forum/septerra_core_legacy_of_the_creator/fix_for_windows_10_works_100

And now everyting works as it should from fix frame rame, mouse and now the videos works ingame.

Thank you very much Arex150 and Runico for all you help :D

Tried this on Windows 10, and it worked like a charm. Thanks man.