I've never done it but my first port of call would be through the Device Manager.
Get to your Control Panel and double-click System then click Hardware then Device Manager. Click the + sign next to the CD/DVD Drive listing and right-hand click the drive. Click Properties, finally clicking the DVD Region tab.
If you enter the make and model in Google, you will get a whole load of websites telling you how to make it so you can play DVDs from any region. It's very simple but they just "forget" to put this piece of information in the instruction books.