Sometimes brand-new 64 bit architecture must be used for running 32-bit programs. You can preserve your 64-bit system and create so called "32 bit chroot" environment. I'll use Debian as guest operating system because it supports easy bootstrapping out-of-the-box.
I assume debootstrap program is already installed. First: create Debian tree:
# debootstrap --arch=i386 lenny /home/dccb/lenny
Then we can chroot to new env and customize:
# chroot /home/dccb/lenny /usr/bin/i386 (...)
Note that shell "/usr/bin/i386" is required for chrooted environment to see 32-bit architecture. If you want to jump directly into plain user account use this command:
# chroot /home/dccb/lenny /usr/bin/i386 su - $CHROOT_USER
Inside chroot you can do (almost) everything (install programs, run daemons, ...). Note that sometimes you will have to change services ports to not collide with services present on host (HTTP, SSH, ...) - it's not a virtualisation, just chroot jail.
Additional note: In order to get correct /dev and /proc tree you have to mount them before chrootting:
mount -o bind /proc /home/dccb/lenny/proc mount -o bind /dev /home/dccb/lenny/dev