How to Detect Someone Else That's Using My Computer
If you suspect that someone else has been using your computer when you are away, you can use a number of techniques to find out for sure. Checking the status of certain files and folders is one of the best ways to detect when others are using your computer and your resources. It is important to find out for sure because someone using your computer without your permission puts your personal information at risk.
Log on to your computer and right-click on the "My Computer" icon. Choose "Explore" from the menu.
Expand the plus sign next to the hard drive and go to the "Documents and Settings" folder. Expand the "Documents and Settings" folder and look for unfamiliar names. The operating system creates a folder for each person who logs on to your computer, using that person's user name.
Click on the "Start" menu and choose "Search" from the menu. Select the "Files and Folders" option. Click on "All Files and Folders."
Choose "More advanced options" and then "When was it modified." Click "Specify dates" and enter the current date. Click search to see any files that have been modified since the last time you logged on to your computers. Look particularly for Internet files, word processing documents and spreadsheets, especially ones with names you do not recognize. This is an indication that someone else has been using your computer.
Check the Internet browsing history on your computer and look for unfamiliar websites. To access your browsing history in Internet Explorer, simply hold the "Ctrl" key down and press the "H" key to open the history window. An unfamiliar website is a classic sign that someone else has been accessing your computer.