Tip molto interessante... soprattutto se date una festa 
...Windows Media Player includes a feature that will let you lock the screen while still making the interface usable, so you can still easily switch music or videos while the screen is locked.
Open up WMP in full-screen mode, and you'll notice a small icon in the bottom-right hand corner of the screen.
...CUT...It's worth noting that if you have screenshot software installed such as SnagIt, the screenshot mode will interrupt the lock mode, so you'll want to close that down before you do this.