This guide is written for Windows 7
-Once logged into your computer, click the [START] button
-Select 'Control Panel'
-Select 'Devices and Printers'
-Right click the printer you wish to use as your default
-Select 'Set as default printer'
Done! Pretty easy eh?
Keep in mind this is only for the user who is logged in, so if someone else logs into your computer they will have a different default printer.