Backing up a complete hard disk is not possible unless you have the right tools.
I use Symantec's Ghost software which takes a complete image of the entire contents, OS, applications etc. and it takes only about an hour or so to complete, depending on your HD size and contents.
In order for this to work, the image must be created on a separate HD, ie external USB drive, such as Archos or Iomega products.
There are other products out there like Drive Image, but I,ve never use them.