This extra program (windows only) can manage multiple proxy settings and quickly switch between them, so you won't have to change proxy settings in Internet Explorer.
Get Proxy Switcher Lite from this site. You don't need to purchase the standard version, free version is ok.
Double click on the file you just downloaded to start installation and follow installation instructions.
After installation is completed, Switch Proxy shows it's icon in your system's tray bar.
Click on the icon. A small window appears, inside click on the symbol .
A new window appears now: