Error : Unable to copy file XYZ.dll. The process cannot access the file XYZ.dll because it is being used by another process
Resolution :
Go to windows command prompt ( Click on Start -> Run -> Type cmd -> Press OK )
Type tasklist /m and Press enter
The above command will list all the process i.e exe and dlls each process is using
Find out which process i.e exe is using the dll XYZ.dll
Then go to Task Manager and End the process