Found my live cd problem, now a question

Hi,
Krister here. I wrote to the list and asked a couple days back about a
problem i had when starting up the Ubuntu live cd. It looked like X
didn't start correctly. It turned out that it didn't, because it uses a
screen depth apparently not supported by my screen. It wanted to use
24-bit color, but my screen wants to use 16-bit color, so my question
is: Is there a way to change the screen depth from the boot prompt
thingy and if so, how?
Thanks a lot for any answer.
-- 
/Krister