My laptop doesn't allow booting from USB and the CD drive has gone bad. It has Windows XP on it. I want to do away with Windows and use Ubuntu only.
Are you sure that your laptop doesn't allow booting from USB?
You may need to enable legacy USB support in the BIOS setup to enable it, then reboot with the bootable USB in the drive, then go into BIOS setup a second time and select the boot devices, looking for the removable drive.
Otherwise, you may have success installing using WUBI, by running the WUBI installer from within Windows. Note that this will install to a small partition within Windows, rather than replacing Windows.