Understanding compiling error responses.

I have been using Arduino since a month. A week ago it was all good with all the necessary libraries. But one day it cant even compile the program it did a week ago. I have tried various versions of Arduino IDE since.

Error -
{

C:\Users\x\Documents\Arduino\libraries\PS2X_lib\PS2X_lib.cpp: In member function 'void PS2X::read_gamepad(boolean, byte)':

C:\Users\x\Documents\Arduino\libraries\PS2X_lib\PS2X_lib.cpp:104:53: warning: narrowing conversion of 'motor2' from 'byte {aka unsigned char}' to 'char' inside { } [-Wnarrowing]

char dword[9] = {0x01,0x42,0,motor1,motor2,0,0,0,0};

^

c:\program files (x86)\arduino\hardware\tools\avr\bin../lib/gcc/avr/4.9.2/../../../../avr/bin/ar.exe: unable to rename 'core\core.a'; reason: Permission denied

exit status 1
Error compiling for board Arduino/Genuino Mega or Mega 2560.
Invalid library found in C:\Users\x\Documents\Arduino\libraries\Ultrasonic-HC-SR04-master: C:\Users\x\Documents\Arduino\libraries\Ultrasonic-HC-SR04-master
Invalid library found in C:\Users\x\Documents\Arduino\libraries__MACOSX: C:\Users\x\Documents\Arduino\libraries__MACOSX

}

Could someone guide me about this please ?