"CANNOT DELETE (...demo.exe file). It is being used by another person or program"

I'm having this problem repeatedly too and it's getting annoying and I
want to know why. It has something to do with permissions, I'm sure of
it. All other files behave normally and under security they have
permissions for SYSTEM, USERS, EVERYONE, and ADMINISTRATORS but they
files I can't modify also have MY account name JOHN there too. We all
have full permissions and they were inhereted from parent objects, but I
feel there is some reason for the error in that the file has my name
from when I logged into the network and wrote that file from a different
machine! I think it wants me to only modify that file from the other
computer. Also, it won't let me delete the JOHN account. I can go into
safe mode/administrator and fix all of this but I want to know what is
going on.

"=?Utf-8?B?ZGFuaWVsN2M3ZA==?="
wrote in :

and is "0" KB (zero KB). When I try to delete the file, an error
appears and states: "Cannot delete warofthering_demo.exe. It is in use
by another program or person. Close any programs that might be using
the file and try again.". I've shut down EVERYTHING but the services
absolutely necessary to operate my system, but it made no difference,