I've recently started playing the gog version of Descent 2 I bought a while back, and I can accept that I'm not the best at the game, but I am encountering a few frustrating issues: it's takes several "mouse drags" just to get my ship turned around, which is a problem when I'm being pummeled by enemy fire, and similarly troubling is how dark so many areas of the maps are, so much so that if I don't have any headlights, I'm just floating in darkness while enemies I can't locate take pot-shots at me.

I've seen several forum posts that say these sorts of issues can be fixed with Descent Rebirth, so I tried installing it. It does let me play the trail of the game, which does appear brighter and easier to control, However, I don't know how to install the "full" game to this mod. The Descent Rebirth website says the instructions are in the download...but I don't see where. So, I would like to know if anyone can tell how to, ultimately, fix my mouse slowness/poor lighting, and/or get the full version of Descent 2 running in Descent Rebirth.

Found it this time! Thank you! The game is running much better now :)

The mouse movement issue is a well known problem, and Rebirth partially solves it. Your ship has a maximum turning speed. If you move your mouse farther than required to spin the ship at the maximum speed, then the excess motion is simply lost. For new users, this often manifests as running the mouse all the way to the other end of the mousepad, getting just a bit of ship motion, then needing to reposition the mouse to resume moving. With practice, you can learn how far to move the mouse to reach maximum speed without wasting motion.

Other games often allowed the player's avatar to pivot instantly if the mouse was moved far enough / fast enough. This feature is often known as "mouselook." One of the Rebirth maintainers finally gave in on people requesting mouselook and added it a year or two back. When enabled, the ship has no maximum turning speed. You can spin the ship all the way around very quickly. If I recall correctly, you need to enable mouselook in one of the game menus. By default, you still have capped turning.

I don't recall many areas that were unacceptably dark. If darkness is a problem, try firing your ship's flares to light up the area a bit. Flares cost a tiny amount of energy, but provide light for 5-10 seconds.