Windows 10/7 dual boot difficulties

[schl1tz]

So I'm having a lot of difficulty installing a dual boot of WIN10 and WIN7 on an HP Probook 6550b. It WAS running WIN7 just fine, but I needed to downgrade to 32bit for some software compatibility. Figured I'd upgrade to WIN10 and just install 7 on a small partition, only to be used to run said software. Did a clean install of WIN10, which went fine. Computer is running WIN10 now with no issues. I created a small 20G partition for WIN7 install. Now I cannot for the life of me get the laptop to boot from the WIN7 DVD media. It just goes right to WIN10 no matter what I try. I was able to boot from the DVD media to install WIN10 without a problem. In hindsight, I now see that I should have done the WIN7 install first, then install WIN10. Can anyone help me to get this thing to boot from the DVD so I can install WIN7? I'm fine with doing a clean install on WIN7 and THEN doing the WIN10 install, but I just can't get it to boot from DVD. I looked for anything even remotely resembling "Secure Boot" in the bios in order to disable it, since that seems to be the problem for a lot of people, but this HP Probook 6550b bios has nothing of the sort that I can find. I would attempt to boot from USB flash drive, but I only have a 4G flash drive, which leaves me 3.7G of space when the WIN7 iso is 3.8G. Ugh. What a pain in the butt.

 

[schl1tz]

Nevermind. Figured out that my WIN7 DVD wasn't actually bootable for whatever reason. I put the WIN10 DVD back in just to see if it would boot and it did. I'm using Rufus to make a bootable USB stick now. Turns out the ISO only needs 3.4gb. I'll be back if I can't get this to work...