OpenBSD does not require a primary partition, nor does NetBSD. Solaris does
for the moment,
although code to fix that has been committed.
I have a Windows 7 x64, OpenBSD, Solaris, NetBSD multiboot. It's not that
difficult to arrange.
I did most of the partitioning in Windows, setting up a primary partition
for Solaris, then logical
partitions for OpenBSD and NetBSD.
Either the NetBSD or OpenBSD media can then be used to edit the partition
types to the
recognised ones. Install as normal, then use EasyBCD to edit the
Vista/Windows 7 boot menu
- modify as appropriate if you're using grub etc or XP..