A lot of storage space used by 'system files' I have a problem of huge storage space missing in my newly bought Galaxy Tab 2 tablet.

It is the 16 GB version, but even after resetting twice to factory settings, the available storage space remains at about 5 GB, with the remaining 11 GB inaccessible, because it is "used for Android system files".

I suspect that there may be back-up or batch files from the previous installations that Android does not remove when I restore to factory settings.

Does anybody know in which directories I should look, and how I can delete the relevant folders to free the expected 6-7 GB of remaining storage space that I need for my applications?
Samsung devices are 'known' for their excessive use of internal memory for Android system files and Samsung's own programs (bloatware?). To free this space you'll need to root the device and put a slimmer ROM on it.

Rooting is a practice which requires some knowledge what you're doing and it will void your warranty. If you have no idea what rooting is, I would recommend you to stay away from this practice since it can not only void your warranty, but also render you device useless (so-called 'brick' it). If you do know what rooting is, then you'll also know which sites to use for this, so I won't tell them here.  Hope you'll understand I'm trying to avoid inexperienced readers from doing things to their devices which they regret. Good luck! :)