You can run 32-bit programs inside a mostly 64-bit system. I run 64-bit programs for almost everything (including the kernel and all system libraries). But I run a pre-compiled x86 32-bit Firefox because the Flash player for Linux is 32-bit only. Same goes for movie playing software, if you want to use win32 movie codecs, which are 32-bit only.

You also have the option of running an entirely 32-bit environment "inside" a 64-bit environment using chroot. This page is interesting: http://gentoo-wiki.com/HOWTO_AMD64#S...ot_environment

Also http://www.gentoo.org/proj/en/base/a...?part=1&chap=2