Hello all,
Sorry for the inconvenience,
It's true what was said by AdminMarak
Def files are libraries for loaders on every platform, deleting these files might cause related functions to not work properly.
It is very possible that the android toolbox cannot open due to incomplete runtime support on the system.
In addition to what is suggested above, especially for systems that have just been installed, I suggest installing the complete all in one runtime which contain all important runtime packages that are necessary to ensure that all any windows programs will work smoothly as shown in the following link.
I hope this helps
