If you're ever worried about what's happening with your PC when you're not around then this is an ingenious solution.

If you've got a USB stick, dod you know you can use it for more than just portable storage? You can in fact use it to block people accessing your PC by installing USB PC Lock Pro and inserting it into any available USB port - nothing more. Once plugged in, it blocks everything from keyboard access to MSN Messenger messages and audio of any kind - so no need to worry about any embarrassing noises whilst you are away from the PC. Once installed on the stick, the upper part of the screen shows the main features such as the Presence and Security Status. Below this are a number of "Plugins" which you can enable separately depending on what you want blocked such as media player, messenger etc. Once set, the program sits in the system tray discreetly so that no one even knows its running.

If you're worried about leaving your PC for long periods of time and have a USB stick, this is an effective and simple solution although obviously, anyone who knows what it is can simply take it out and access whatever they want to.