(SOLVED)No root file system defined

I try to install Zorin 8 Core/Lite to a 16 Gb USB drive. I will make a "Full install" from a DVD or an other USB using "something else", All goes ok. until I hit the key "Install now" then appears a Window telling "No root file system defined" I have tried to format to fat32 and ext4, also setting a bootable flag to USB partition, no difference. The window tells that "Please correct this from the partitioning menu". Do not know how?

For clarity reasons the process was following:
- I erased and formatted a USB drive to fat 32 or ext 4 format
- I used a .iso file from DVD or alternatively a USBlive installation as cource
- I booted from there and selected install ethernet connected to net
- I selected the alternative " something else " and there the USB /dev/sdb and there the only partition /dev/sdb1
- selected the device for boot loader installation /dev/sdb1

Then I hit the key "install now" and then the window appears.

Hi,

you must set the " / " (root mount point) otherwise the installer doesn't know where root is to be set, if you only have the one partition, then that will be root mount point!.

Yes, now it started to load the files! Fine untill now. Now I booted Zorin 8 Core from USB and seems to start. Runs very nicely, it is a USB 3.0/2.0 16 Gigs drive I use in a USB 2.0 port. The advantage is that there you can make full uppdates. The disadtage is that it takes ca 3-4 times more space from USB and it is not portable like a USB live installation.