How do I know my backup is working?

When all is hooked up and the backup is done it shows a long group of letters and numbers under which are the file directories. I must look through each of these through Windows Explorer to see what is there. I can look at the date modified but they do not seem to change. Should the modified dates change? I have several drawing files from Pro Engineer on my system, but I do not see them show up in Explorer. How do I know that they are there, I need these backed up.

Thank You,

Dale McKillips