"No root file system defined" error while installing ubuntu

Make sure that the partition file system you wish to install Linux, Ubuntu or Backtrack on it is ext4, ext3 or ext2, and not FAT32 or NTFS.

Then mount / on it:

1. During the installation process press "change" on the partition you wish to use

2. Make sure "do not use this partition" scroll is not chosen, scroll to ext4, ext3 or ext2

3. On the "mount" field write /

4. Click ok, then next a message will appear saying something like "swap area was not defined, do you wish to continue or choose a swap area?", click "ok" and continue or click "go back" and choose another partition and click change, on the file system scroll choose "swap" and click "ok" and next

This will solve both "no root file system is defined" and the "swap area" message, if you still get the swap area message then on step 4 mount /swap to the partition

To answer your first question, the partition proposed to be split on the first screen was your windows partition. Since you already have created a partition for Ubuntu, you don't want to do that.

You say that you selected the partition on the advanced screen, but simply clicking on it does nothing; you need to click on the edit button and assign the partition a filesystem type ( use ext4 ) and mount point.

The error is because you did not assign any filesystem to be mounted in the root directory ( / ) and therefore, there is nowhere to install to.

continuing from @binW's answer,

If you are ready for some adventure, which might become a nightmare if proper caution is not followed.

You need to define the mount point specifically as / for it to function as root file system.

Swap you can keep, but literature tell you to keep it!! FYI, I don't have a swap.

Image source