A workaround for computers that don't boot from some CDs (like the Simply Linux 6.0.0 beta CD -- https://bugzilla.altlinux.org/show_bug.cgi?id=26043#c3 ) is to install Smart Bootmanager onto the harddrive.

This is a workaround once and forever: in the future, Smart Bootmanager will be useful to boot any CD.

Smart Bootmanager is referred to in
http://syslinux.zytor.com/wiki/index.php/ISOLINUX#What_to_do_when_nothing_works... .

Smart Bootmanager -- http://sourceforge.net/projects/btmgr/files/ ; but it
seems that the source doesn't compile now (with modern nasm etc.)...

Debian (and Ubuntu) has a package with it -- http://packages.debian.org/squeeze/sbm .