If you want to quickly lock yourcomputer while working when kids or strangers hover around, here's a shortcut to do that.
1. Right click on the Desktop and select New -- Shortcut
2. Enter rundll32.exe user32.dll, LockWorkStation as the shortcut
3. Call it Lock Computer and right click and choose Properties
4. Now Click on Change Icon and search through shell32.dll to set any icon you want. Remember you need a password to do this!