It fixes windowed mode for non-16 bit desktops, allows movies to run without needing to use the compatibility settings, gets rid of resolution switching in fullscreen, and (optionally) stops it hogging so much cpu time. There's also a couple of UI tweaks: you can middle click to run and follow the cursor, and click again to stop, (slightly easier on my fingers than double-click-and-hold) and you can right click on the portraits in combat to queue up a next move. (i.e. the character will automatically be selected when the next section of their endurance bar fills up.)
Movies need converting from quicktime format into something directshow can understand. The patch installer will do it automatically if you have quicktime or quicktime alternative installed. If not, you can use something like rad game tools to transcode them manually. Converting the movies to a different format would have made more sense for GoG to do themselves rather than me, (and would have cut 70mb from the download size,) but it's a bit late for that now, and I couldn't get the quicktime movies to play nicely with non-admin mode, so I didn't have any other choice. :(
Tested only on the GoG version of septerra core, and only on windows 7. Windows xp (sp2+ only) and vista probably work, but anything earlier wont. Likewise, disc versions of septerra core updated to 1.04 will probably work, but 1.02 or earlier wont. I'm not particularly far into the game yet, so I may have missed stuff. I'll probably make updates as I go along and bump into more things that annoy me. Finally, since this has so far been tested on exactly one computer, by one person, with one hardware/software configuration, and only for a few days, YMMV.
Grab from near the bottom of the left hand panel here.