RPG Maker games are pretty hard to make run smoothly. I've heard some people reporting improvements by running the game on only 1 CPU core. The logic being the older RPG Maker engine is more suited/optimized to run on a single core.
Here's how you would make the game run on a single core:
1. Start the game
2. Open task manager and click on the "details" tab
3. Right click on the Reborn .exe that's running and select "Set affinity"
4. Uncheck all the CPU cores except for one of them
5. Select "OK" and close the task manager.
You'd have to repeat this process everytime you launch the game, or you could make a batch (.bat) file for it. Try it out, and if you find that running the game on a single core works well for you and would like to create a shortcut, here's how you can make a .bat file to launch the game using only one core.
Create a text file (with like, Notepad) and write this:
So in my case it looks like this:
The first line browses to the directory of the game file, and the second line, "start /affinity 1 Game.exe", will launch Game.exe to run using only Core 0.
Save the file as a .bat, and that's it. Double click to run. I made this in my Reborn folder.
Now, you can't pin .bat files to the task bar (where I like to keep my Reborn shortcut) but there's an easy workaround if you want to do that.
Create a new shortcut (I also made this in my Reborn folder), and in the target location write: cmd /c "[path to batch file]"
So mine looks like this:
Name it and change the icon to match Reborn's icon so it looks pretty and you're done. You can pin this shortcut to your taskbar or start or wherever you have you current Reborn shortcut.
Hopefully this was followable, and hopefully you see performance improvements with this. Otherwise there's not much else you can do AFAIK besides buying a beefier computer :p