My next attempt is to change the boot priority order within my BIOS for each of my 3 hard drives. I recall having done this before... hmm.
Yes. Indeed, this fixed the problem.... ALMOST. I am now getting the Sabayon bootloader with the options I specified within the installation. The weird thing is, because I decided to add both the 64 and 32 bit drives, it got wonky on me such that if I choose the 32-bit one that I added, it gives me the dreaded:
"BOOTMGR is missing"
"Press Ctrl+Alt+Del to restart"
Otherwise, if I choose the 64-bit option (that was the regular Windows boot option given in the Sabayon installer before I renamed it to add my other drive) it redirects me to the Windows Boot Manager that I used to see. And from there can happily pick either the 32-bit or 64-bit Vista. This last weird issue is probably my fault, since I decided to add an entry to the drive, not knowing what the result would be. So I guess all that needs to be done now is to remove the unneeded entry in the bootloader and I'll be ready to go... Now I just have to figure out how to do that in Sabayon.
Mmmm. Triple Booting. Delicious.