Hello has all I have just launched my unreal today and then he tells me this :
I already have to reinstall nothing to change 
In our experience this is usually down to a corrupt blueprint that was fine until you closed Unreal. If you’ve created or edited any structures, or deleted any files without replacing references recently, see if you can undo the change and see if it’s still crashing.
I have absolutely to delete nothing
Hi iKyOo,
What version of the editor do you have? Does this occur with a blank project with no additional content?
I open no project and I use the version 4.7.5
Please verify your editor by going to the launcher>library and, using the dropdown arrow next to your engine version, press “verify”. Additionally, if you have a project on your machine, go to the project filepath and open the .uproject directly. Does the project open when you do this?
“using the dropdown arrow next to your engine version, press verify” when he is finish i launch my unreal and he give me that :
And i don’t have project for open 
Go to your engine filepath and try opening UE4Editor.exe directly from the binaries folder. The filepath should be:
\Unreal Engine\4.7\Engine\Binaries\Win64
See if you can open it by going directly to the editor .exe as opposed to using the launcher.
My EU was in another hard disk I have him to move in head teacher maintaining its working thank you anyway:)
Hey,
this issue tends to occur when environment variables exceed maximum allowed lengths. Check how long PATH is, if (after expanding) it’s over 2048 try to reduce that and see if it helps. If it doesn’t, check if any other variables have outstanding lengths. From what I checked, Windows sometimes required to log off and log in again to properly envvar propagate change visibility.
Hope that helps,
Cheers, Mikolaj