CareUEyesLite, the free version, allows you to quickly control the brightness of the monitor from the drop-down menu located in the program bar next to your Windows clock. It can be set to 200%, 40%, 60% and 80%. You can adjust brightness quickly with one click when your lighting is low.
CareUEyes Lite takes up only 600KB of RAM and is very easy to use on any type of computer. You can purchase the PRO version from the Windows drop-down menu if you wish to have access to a wider selection of options.