HI COULD SOMEONE PLEASE TELL ME WHAT THIS ERROR MEANS?
Arduino: 1.8.5 (Windows 10), Board: "Arduino Duemilanove or Diecimila, ATmega328P"
Build options changed, rebuilding all
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: File exists
exit status 1
Error compiling for board Arduino Duemilanove or Diecimila.
Those boards are pretty old. Are you sure that's what you're using? What happens if you select Uno or Nano for the board? Also, I'm more used to seeing the path being ...\hardware\arduino... than ...\hardware\tools... but perhaps your set up is much different from mine.
I'm more used to seeing the path being ...\hardware\arduino\
hardware/tools is the normal toolchain location when using the Arduino AVR Boards hardware package included with the Arduino IDE, as jenny13 is doing.
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: File exists
This sort of error could be caused by your antivirus software. Try TEMPORARILY disabling your antivirus for a single compilation to see if the problem goes away, then turn the antivirus back on. If the problem doesn't occur with the antivirus off you will need to adjust the settings of your antivirus to whitelist the appropriate file, folder, or process so it doesn't interfere with compilation.