Windows 7 on iMac using Bootcamp**HELP**

I've been trying to install Windows 7 on my 2011 iMac (i3 core). The internal superdrive no longer works - it only accepts CDs - when ever I insert a DVD it gets ejected after a few moments. This iMac is out of warranty and no AppleCare was ever purchased.

I've also tried creating a bootable USB iso, but when ever I go through the Bootcamp process and the computer restarts to begin the Windows install process I get the message 'Insert Boot disc and press any key to continue'. For some reasons it doesn't see the USB iso. I've also tried using a Seagate 250G FreeAgent drive I had laying around by turning it into a bootable iso, but had the same 'no boot disc' issue.

I purchased an external DVD drive (Samsung), but again when I go through the Bootcamp process and the iMac restarts to begin the Windows install I get the same no bootable disc even though the windows install DVD is inserted in the external DVD drive.

I'm at my whits end and frustrated with Apple... this iMac is under 3 years old!

Any help with this install...?