This is one strange Windows 7 quirk! Lets say you use the Windows 7 Backup utility to perform a backup and save the files on to your hard disk. Now IF you use this Windows 7 Backup utility again to perform a backup for a group of files that are LARGER than the first group of backed up files, the back up may take a real long time … even upto 16 hours for 400 GB of files!
Windows 7 backup takes lot of time
Microsoft has confirmed that this is a problem in Windows 7. Now why does Windows 7’s backup utility behave this way? Err … no idea! But hey, a fix is available to remedy this problem, if your Windows 7 Backup Utility is behaving this way!
Head over to KB2283445, download the HotFix there and install it.
You might want to also check out some free Imaging, Backup and Recovery Software for Windows.