I installed Ubuntu. Now I get:
"fatal err. not os detected.
I cant boot from dvd either
What can I do?
Without knowing exactly what you did I would guess you have broken your boot loader.
Look at this question and try the second method How can I repair grub? (How to get Ubuntu back after installing Windows?)
boot from live cd and run these commands
sudo add-apt-repository ppa:yannubuntu/boot-repair && sudo apt-get update
sudo apt-get install -y boot-repair && boot-repair