Restore Windows Vista cannot find any of my backup files

I just finished restoring my HP Pavilion PC to factory settings, and it works great now. During the restore process I was asked if I wanted to backup my files, and I connected an external hard drive and watched for 8 hours while it backed up everything. My problem now is that I cannot find any of my backup files on the external hard drive. What did I do wrong? Is there any way to restore my files]?