Most good backup programs will allow you to do incremental backups, so only backing up files that have changed since the last full backup. Check this out:
http://www.pcpro.co.uk/reviews/softw...mage-home-2011
I have used Norton's Ghost before so check this out as well.
http://www.pcpro.co.uk/reviews/softw...orton-ghost-15
You also have a backup built-in to Windows: When you use the Back Up Files wizard, Windows keeps track of which files and folders are new or modified. Then, when you make a new backup, you can back up all of the data on your computer or just the files that have changed since the last time you made a backup. If you set up automatic backups, Windows regularly backs up your files and folders so that you don't have to remember to do it.
Hope this helps.
ps Windows 98 use to have a great backup program, which backed up any file that you changed so you could recover almost anything including databases, but due to litigation had to remove it. I recovered DataEase databases after rewritting new code that caused a problem.