Windows 8 Scheduled Maintenance
Windows 8 can run common maintenance tasks – software updates, security scanning, system diagnostics and more at a scheduled convenient time, which is good.
Unfortunately it doesn’t actually ask you what time is convenient, instead just setting it to 3am and allowing the system to wake your computer (if hardware and circumstances permit) to do its work. Which isn’t so good.
To change this, launch Control Panel, click System and Security > Action Centre > Maintenance. You can now click ‘Start maintenance’ to launch any outstanding tasks right now, while selecting ‘Change maintenance settings’ enables you to choose a more convenient time, and optionally disable the feature’s ability to wake up your computer if that’s not required