I can confirm that Jfabiano's method works (I used command prompt)
Basically what I did was use the type command to list everything in the .dat file and moved it completely into the other dat file by using >.
Here is an example I used.
NOTE: If you have anything in the directory with a space make sure to put quotes around it, for example: "C:\Users\mderryberry\AppData\Roaming\Avorion\galaxies\old dedicated_server\player_1.dat"
I can provide a video if need be as well to show that it does work. But I think people can figure this out for themeselves, thanks!