windows 7 backup hangs at 57%

I am trying to backup to an external hard drive, 120gb. The backup starts fast and then hangs at 57%. I have let it run for several hours and still only 57%. I have a new hp p6350z pavilion computer with a 454 gb with 420 gb free. The external hard drive has been reformatted prior to attempting the backup. All of the literature I have found does not say that the backup hard drive must be equivalent to the computers hard drive.

What files system was used when reformatting the external hard drive?

While you are exploring other options, if this is a USB device, try changing ports.

I use NTFS

Try a different backup program and see if it is any different - you can get a full working trial copy of Acronis True Image from here:

Acronis True Image Home 2010 - Download Acronis True Image - Download.ba