ubuntu 11.04 on dell vostro 260

[en3o]

I would like to install ubuntu 11.04 on dell vostro 260. The computer boots from the CD, choose install options on the disk, and here the problems begin.

stdin error 0 ubuntu
init line 7 can't open dev sdb no medium found no medium found
init line 7 can't open dev sde no medium found no medium found

After a few moments, it displays

(initramfs) Unable to find a medium containing a live file system

Does anyone have any idea how to fix it ?

[nothingspecial]

Changed prefix from "lubuntu" to "ubuntu"

[critin]

choose install options on the disk, and here the problems begin.

You may have a bad download or burn. Did the burn program check the download for completeness?
Can you get the 'Try Live' option to start? If so, try it live and check the disks from gparted, then install from the desktop icon.
If it won't install from there, download and burn a new copy.