Hard Drive Full???

[Şerban S.]

[...]
I have no idea why hard drive has filled up again or with what.No idea where to even look. [...]

Hi!
Use GParted to see what happens.
If there is something wrong, you should see that /dev/sda1 is almost full.
Install then QDirStat and when it starts, put into the dialog that shows, "/" (without quotes).
This lovely App, QDirStat, will then show you all dirs and the the occupied size of each dir.
In GParted, you should see at most 13 GB occupied by the Linux Lite.
If you use a /home partition, the size of the occupied space on /dev/sda1 should be even smaller (6 - 8 GB).

You can use either the program shown above to clean whatever needs to be cleaned, or BleachBit.
If still in trouble, than the only solution I see, is repartitioning the HDD and reinstalling everything from scratch.
For me is easy, because I use low level backups if things go sideways. Takes less than 20 mins to restore both Root partition and /home partition.
I'd also suggest you use the "hdsentinel" program, to check the state of the HDD. It looks to me that this is a possibility there, too...
As an alternate solution (although I strongly recommend hdsentinel), you can use

Code:

sudo /usr/bin/gsmartcontrol-root

or launch it from the menu.
If it's missing, then install it via Synaptic or CLI.

Or maybe...
Since the info you provided tells me nothing, I have to consider another possibility...
Did you previously use Windows on this HDD?
Because if so, there is a very high probability that you have a HIDDEN partition, that stores some Windows backups. That is why I suggested you to use GParted.
If this is the case, than DELETE the partition. It probably has all the "missing" space inside.
You can then reassign the space, either to /dev/sda1 or create a new partition, of your choice.

Good luck!