Hi, for a definite backup of your computer, rather than keep using the backup manager that comes with Zorin, I would recommend a free package and a paid for package - the free one is redobackup from
http://redobackup.org - please be aware that this is only able to backup the entire drive which it compresses - for example I made a backup of Windows at work which was on a 400 Gb drive - the image was 50 Gb sent to external drive - a forum member pointed uot that redobackup is unable to backup individual partitions but for a free tool that is simple to use its a nice little piece of software. The paid for option which has more options is Acronis True Image (Home Use) from
www.acronis.com. Other than that what I tend to do is to simply backup my entire '/home' folder after pressing 'Ctrl+ H' to ensure hidden files get backed up also - in all scenarios you need either an external drive or a second hard drive installed in a desktop for backups. Hope this helps!
