How did you burn the ISO to DVD? What burn software did you use? When you look at the DVD's contents does it only contain a single .ISO file or is there a Setup.exe file?
If there is only a .ISO file then the image was not burned properly. (See how
HERE. Links to IMGBurn are available in our
freeware DB.)
If there is a setup.exe then try running it to see if it starts from inside Windows; if so then it's not the DVD itself.
If setup.exe runs when tested above then ...
What it sounds like is the drivers for your actual DVD drive are not being loaded correctly into memory when you use the Boot Menu option. What you might try instead is to go into your BIOS and set the boot order there making the DVD drive first.
Another question ...
Do you have multiple OSes on your machine, for example Linux, or is W7 the only OS on your machine? Multi-boot systems can have their own issues which is why I ask.