You had 2 HDDs and each had a OS on them.......correct? If so, all you need to do tap F12 to bypass the bios screen and the boot menu will pop up. From there select the HDD/SSD you want to boot from.
I used to use the Mult-Boot option all the time......The key to doing this is not have the Primary C drive connected (unplug cables of drive) when installing a 2nd OS. I had windows on C drive then had 2 more HDD's, one had Ubuntu and the other had Zorion. The only draw back to this is and this is ture of dual booting, you have to restart to change the OS.