I'm installing ubuntu-12.04.3-desktop-i386 using CD on Sony notebook. when the installation goes to about the end (90%), system crashed. when I want to reinstall the system, CD-rom just can't run any more. what can I do ? Thank you!
Load the necessary drivers required for CD Rom to run again (using the windows 7/XP that you received with the Notebook) & then try to install it again.
How to Load CD-Rom driver ?
Insert the CD and press F6 (in case of XP) which will load the necessary drivers needed to run the CD-Rom and then try to install Ubuntu again.
I suggest you first live boot the Ubuntu CD and then install it from there (using the icon present on the desktop in live session).