Any two operating systems can reside on the same boot able hard drive partition.
There is only one rule though.
Any operating system of a lower version must be installed to the boot able drive first.
You can then install a higher OS version after it and have a dual booting OS drive.
But you cannot install a lower version of an OS if the existing one super seeds it in version number.
Weather you have a 32bit os or a x64 bit os pre installed.
It`s a pain I know, not sure about trying to install an x64 bit version of windows 8 with windows 8.1 already installed.
to be honest, but i suspect it will have a winge when you try to install windows 8.
An example is if you had windows 8 say, and wanted to install windows 7 it would prevent you from doing so in most cases when you begin the windows setup from Cd/Dvd. Or when you click next to install the OS.