If you're installing Ubuntu on a machine with an IDE cdrom and an SATA hard drive, the following information will be extremely helpful.
Stollen from here: https://bugzilla.ubuntu.com/show_bug.cgi?id=1440
insmod /lib/modules/2.6.xxxxx/kernel/drivers/cdrom/cdrom.ko
insmod /lib/modules/2.6.xxxxx/kernel/drivers/ide/ide-core.ko
insmod /lib/modules/2.6.xxxxx/kernel/drivers/ide/ide-generic.ko
insmod /lib/modules/2.6.xxxxx/kernel/drivers/ide/ide-cd.ko
insmod /lib/modules/2.6.xxxxx/kernel/drivers/ideide-core.ko
UPDATE The original post was wrong. The above is now correct. Unfortunately the info in that bug fix was not quite 100%