How do I reset Ubuntu? [duplicate]
Your computer will not boot from DVD then you have one other option. Booting your computer from USB memory stick. You can use many softwares to achieve this, but I personally like UNetBootin which supports windows, mac and linux. You will need to have a ubuntu ISO file that you want to install, and a suitable usb memory stick (above 4GB storage is fine). Create a bootable USB stick. Configure your BIOS to boot from USB and reinstall.