Why so many? Just use Win 7 64 bit & Ubuntu.
Win 7 gives you a few options for running 32bit Applications, like Compatibility Mode, or Windows XP Mode for some older productivity applications that will not normally run on Win 7.
Since you're using two drives, you have a couple of options for booting.
1. You can keep both drives plugged in and install both of your OS. Instaling each OS one its own hard drive. This will give you a boot menu and let you choose between which OS to load.
2. Unplug on drive - install your first OS - Unplug the first drive and plug in the second one and install the second OS. When choosing this option, you have to choose with HD to boot from during the system startup. This option also keeps your second OS hidden. If you just let your system go through it normal boot up, it will always choose the first boot device that you've selected.