well, you can use EwfCommitFile in the EWF API but it only works on files that don't change in size. You can also search the OS forums for an old thread of mine where I describe creating a fixed size virtual disk that you can then write any number of files into. Since the virtual disk is fixed size you can then commit it and maintain state.

Otherwise you can use FBWF File Based Write Filter, but I haven't gotten around to write a tutorial for that.