If you're running Vista Basic or Vista Home Premium and you want to restore your files to one of the backups your shiny new OS has been making, do you know what you need to do? Upgrade. Yes, the cheapo versions of Microsoft's new OS make backups of your files using the Previous Versions feature, but you aren't able to access them without upgrading to Vista Business, Enterprise, or Ultimate.
The wussier versions of the OS do back up system files for the system restore feature, but the previous versions feature that creates backups of your other files is crippled. That means if you accidentally save over the novel you've been working on for the last couple of years, in order to restore to last week's version you'll need to first upgrade to the $400 Vista Ultimate. How nice.