booting to login screen, or bringing up desktop?
Does it take too long to get to a login screen from power-on, or just too long to bring up the desktop after you login?
If it's the second problem, use a lighter window manager, like IceWM instead of Gnome or KDE.
If it's the second problem, perhaps you should go to a distribution that is more nearly optimized to your hardware. I was under the impression that RH was i386-optimized, while Mandrake was i586, and things like Arch linux or gentoo were i686 and above optimized.