How to log activity on my computer?

To stop your mother playing games on your PC at 3 a.m. use Parental Control

After you've turned on Parental Controls for your child's parent's standard user account, you can adjust any of the following individual settings that you want to control:

Time limits. You can set time limits to control when children parents are allowed to log on to the computer. Time limits prevent children parents from logging on during the specified hours. You can set different logon hours for every day of the week. If they're logged on when their allotted time ends, they'll be automatically logged off.

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In the Family summary window, click Edit settings for the user account or accounts for which you want to customize settings. You will then be able to:

• Set the desired level of web filtering to determine what types of sites can be accessed.
• Review the websites your child mother has visited, games played, and time spent on the computer.
• Manage your child's mother's contacts in Windows Live Hotmail, Messenger, and Spaces

You can also try a time monitoring program, like Manictime (which I personally use in its free edition) or others.

They will usually log all activity, which programs and websites are used, when, and for how long. Some of them can be hidden also, if you don't want an icon in the systray.