My setup is similar to yours - 2 PCs and 1 USB external hard drive. Without knowing more specifics about your configuration, it will be near impossible to give you "simple" instructions.
Remember one thing - SyncBack is intended to backup/sync user data files, not programs or the OS. So, saying that the HDD's in the 2 PCs are 80% the same is irrelevant.
I set up my Profiles to backup/sync the important data files on my PCs. Each one was carefully thought out. I created each individual Profile, then a Group Profile which runs them in a specific order.
Here is a screenshot of my Profiles which may give you an idea of how you need to approach your setup.
![Image]()
Full image here: http://i61.tinypic.com/2dmb7nq.jpg
Remember one thing - SyncBack is intended to backup/sync user data files, not programs or the OS. So, saying that the HDD's in the 2 PCs are 80% the same is irrelevant.
I set up my Profiles to backup/sync the important data files on my PCs. Each one was carefully thought out. I created each individual Profile, then a Group Profile which runs them in a specific order.
Here is a screenshot of my Profiles which may give you an idea of how you need to approach your setup.
Full image here: http://i61.tinypic.com/2dmb7nq.jpg