OK, so just to report back, I have a perfectly good Win7 install on one partition, and a perfectly good OS X install on another. I am using the Windows bootloader to boot with EasyBCD helping with the Mac boot. I dl'd the VMWare Fusion trial and when I ran it it recognized the Windows partition as a BootCamp partition right away. On first boot, it seemed to attempt to install VMWare tools multiple times (?) but worked out in the end. So now, it boots fine, but runs pretty slow, and I have yet to get networking to work, even though it works fine when booted as a Windows machine.
Couple of oddities-- when it boots, it of course presents the same boot menu which includes MacOS. I've been afraid to try it. Perhaps I should change my default back to Windows to be safer. Also, when doing an honest hardware boot, the Windows loading screen is the Vista version, but when booting through VMWare, it shows the prettier Win7 version. That should be a clue to me as to what's being loaded from where, but I am not quite getting it. There were multiple repair steps etc getting this going.
Anyway, summary is that Fusion recognizes a Windows partition on this machine as a BootCamp partition.