There is no way that a new laptop would have a full hard-drive unless you immediately moved a ton of files over to it. But then again, any laptop now would not have Vista unless you posted in the wrong section. Is this a used one you got? If you open My Computer, right-click on the hard-drive, what does it tell you for space usage?
Did anything else happen before this started? You can try to do a Windows System Restore http://windows.microsoft.com/en-US/windows-vista/System-Restore-frequently-asked-questions