I have this idea for a free backup application.
The largest problem I need to solve at the moment is how to access files which are being used or are system files. I would like the application to be able to perform a full backup of files (i.e. not on a disk sector by sector level).
I'll turn the server part of the application into a service. First of all this service will need to be run with administrative privileges I guess? And secondly, is it possible to access locked files and files used by the system? Maybe take those files after the next reboot? (I've seen some anti virus applications work that way.)
I will use C# and the .NET platform, as it seems to be the easiest way to develop Windows applications these days.