Yes, you can. In theory, doing a custom install and placing Office 2007 in a completely different folder will do the trick. BUT... don't install more than one copy of Outlook or Access. I found that the double copy of Access caused problems, and I have heard the same for Outlook. I guess it's because those two apps are heavily integrated into Windows?
Probably the best solution if you want to set it up, is dual-boot. That way there are no conflicts. Another option (and the one I use now) is to install VirtualPC 2007 with another copy of Windows, and install the new Office in there. No conflicts, but you need enough RAM to make it usable.
Denis