Running a 64bit and 32bit fedora at the same time

[Harald Grossauer <harald grossauer uibk ac at>]

I have an Athlon64 system with FC4-x86_64 running. For several reasons I
also would like to have a FC3_i386 system running at the same time. How
can I do that?

I tried to use Xen (the 3.0-unstable-x86_64) but it did not work (could
not find my root partition after the xen kernel was loaded, probably due
to missing SATA support in the kernel). Neither could I compile Xen-2.7
myself (gcc4 complained about a struct with unkown length, gcc32 issued
a warning which is treated as an error in by the xen Makefiles).

So I created an ext3 filesystem in an ordinary file and mounted it. Then
I thought I could install FC3_i386 into that file so that I later can
chroot into it. But since the installer (autorun) of FC3_i386 needs to
be root I am afraid that it messes up my currently runnning system.

Do you have some links, help or additional information for me?