Just to be clear, this is only for the LiveCD and getting to the desktop in 10.04
Once there I am not sure what you would have to do if you install and want to make this a permanent install.
So, here we go:
Put the LiveCD in and boot up;
when you see the Ubuntu logo hit Enter;
Choose language and leave the default Try as a live cd or whatever it says again;
Important: hit F6 and then Esc to see the boot line
file=/cdrom/preseed/ubuntu.seed boot=casper initrd=/casper/initrd.lz quiet splash --
Now, again this is important, move the cursor backwards and remove quiet splash;
Add the following parameter:
In other words, the boot should look like this:
file=/cdrom/preseed/ubuntu.seed boot=casper initrd=/casper/initrd.lz i915.modeset=1 --
Now hit Enter and hopefully you will be at the desktop admiring Lucid Lynx 10.04.