Microsoft informed that in certain scenarios users of Windows 7 that attempt to Shut Down, or put their computer into Sleep mode, won’t be able to do so. “When the system is under heavy load, you may encounter one or more of following problems: hotkey on your keyboard doesn’t work. For e.g., you press hotkey to control brightness of your computer screen. However, level of brightness doesn’t change.” Windows 7 stops responding when you shut down computer or put computer into Sleep. This problem frequently occurs on computers that have multiple processors or that have a processor with multiple cores. Affected users can download a hotfix from Microsoft, said KB977307.