The next step is collecting the files you want to backup. RAR is a good tool for that. It can put all your files into a single archive file and it can take the directories to be archived from a file list.
So create a file in which list in separate lines the directories you want to backup and then create a batch file with a command like this:
"C:\Program Files\WinRAR\Rar.exe" u "c:\My Dropbox\backup.rar" @c:\backup_file.list
This command reads the list of files to be backed up from c:\backup_file.list and puts the result in the Dropbox directory. The command u means the archive will be updated, so only files you change is written to the archive if you run the command again and again.
Because that is what you should do and you should do it automatically, so run the batch file daily with the Task Scheduler.
Are we ready? Almost. If you want to secure your stuff (and why wouldn't you?) then you should encrypt your backup file. RAR can handle this too easily, just add two more switches to the command line in the batch file and replace password with your own encryption password:
"C:\Program Files\WinRAR\Rar.exe" -p"password" -hp u "c:\My Dropbox\backup.rar" @c:\backup_file.list
That's it. It backs up your files, encrypts them and uploads the backup to the cloud with Dropbox. And with the help of the Task Scheduler all that happens automatically. Isn't it a great thing?