Got pointed to this tool SyncToy from Microsoft the other day and its is terrific for ensuring that all the files are copied onto drives. Its free and can be used to copy just the modified files from a working directory to external drives or other machines.
I have used it for a week and cannot fault it - saved me a load of time.
Find the overview here.
Did I mention it was free? Well it is free.
Roger
http://www.microsoft.com/downloads/d...displaylang=en