I was comfortably using the ARDUINO IDE v1.8.0. But for some stupid reason I wanted to check v 1.6.13 While I tried to install this older version, during uninstallation of 1.8.0 some thing went wrong and an error appeared.
Error opening file for writing: C:\Program Files(x86)\Arduino\hardware\tools\avr\lib\libavr-sim.a
Now I am unable to uninstall and reinstall neither v 1.8.0 nor v 1.6.13. I am using windows 8.1 Urgent help needed please.