Setup Error: end kernel panic - not syncing: vfs: unable to mount root fs on unknown block(2,0)

I solved this problem by changing the ubuntu setup containing usb's format from NTFS to FAT32

On Windows, go to My Computer, right click on the USB disk on which you want to add the Ubuntu set-up, then select format and a new window will open. Change file type from NTFS to FAT32 and click start.

After this process, you can continue your Ubuntu Installation with USB

This apparently can also happen after a bad install. The simplest thing to do is to remove your usb from the target system, format it again (via a source system) to FAT32, recreate your Live USB and then rerun install. This fixed the issue for me and installed successfully for Ubuntu 15.04

Regarding the previous answer, I would like to share my recent experience with this same condition/error message.

I passed through it while trying to install the Ubuntu 14.04.2 LTS for Desktop from a USB media. In my case the previous message did not make any sense because my USB media was formatted with FAT32.

After a short research, reading of this version requirements I perceived that my computer did not fit the minimal amount of memory required (3 - 4 GB). As my desktop just have 2 GB of RAM, I downloaded to 32-bits version and the installation was an accomplished without further problems.

Best regards.

Murilo pugliese.