On some 64 bit PC that we have tested, there are some error with the serial port driver that cause Arduino IDE to have very slow response especially when you click the Tools from the Arduino IDE top menu. If you already have your Arduino IDE downloaded and ready in your PC, simply run the Arduino IDE, and try to click the tools from top menu. If you get the dropdown menu after more than 10 seconds, then you will have to follow this guide for the rxtxSerial.dll Fix.
Download the attached rxtxSerial.dll zip file at the end of this article, and unzip it. You should get 2 files extracted from the zip file, one “instructions.txt” text file, and the other one “rxtxSerial.dll” file. Copy this ‘rxtxSerial.dll” file to your Arduino folder, and replace the old “rxtxSerial.dll” file. Before you copy, make sure your Arduino IDE is not running, and it is advised to have the orginal “rxtxSerial.dll” backed up (simple rename the original dll file to “rxtxSerial_backup.dll”).
After the fix, try to run Arduino IDE again, and this time you should have a smoother Arduino IDE. Clicking on Tools menu will give you immediate dropdown menu, and the startup time for Arduino IDE will also be faster. It also improve the program loading time for Arduino IDE.