we can install ubuntu 12.04 but it disappears once we restart it and model is inspiron 5423 ultrabook. I am trying for a dual boot version, i mean to run ubuntu along with windows
If you are booting from an Ubuntu live CD/DVD or live USB flash drive and running the installer, and it appears to succeed, but when you remove the installation media and restart you just boot into Windows without an option to select Ubuntu, this usually means the GRUB2 boot loader was not properly installed to the Master Boot Record.
The solution to that is to reinstall GRUB2 to the MBR. You can choose whichever method you prefer. Because they're easiest, I recommend either using the Boot Repair GUI utility or using this method.
If that doesn't work, then we definitely will need more information to answer your question. Here's the information we need:
- How, exactly, did you install Ubuntu? Provide as much detail as possible.
- In particular, if you installed Ubuntu inside Windows using Wubi, the above instructions will not help you, and you'll have to tell us that.
- Boot from the live CD, open a Terminal window (Ctrl+Alt+T), and run
sudo parted -l. Select all the text in the Terminal window, copy it to the clipboard, and edit your question, pasting it into your question and formatting it with the <$> tool in the Ask Ubuntu editing toolbar. (You should be able to access the Internet from the live CD system to do this.)