WINDOWS 7 efi - no CD drive

It's much better to install Classic Shell, which makes it look much more like Windows 7, than installing Windows 7. It saves you the hunt for Windows 7 drivers (not sure those even exist!) and it doesn't void the warranty.

But if you're sure you want (and the owner, your work, doesn't object), I'd first buy an external DVD-drive to boot the install disk from. Then you don't have the troubles with making a bootable USB.
And then you have to tell in more detail all things you tried and how they failed.

Kees

If this is a work system, installing another OS on it aside from the one provided, without permission, can be a great way to get yourself fired. Hopefully you haven't done anything irreversible yet like wipe out Windows 8, otherwise you'll likely have to own up to what you did which might well be followed shortly by packing up your things and starting the search for a new job.

is to install Oracle's Virtual Box program, then install Windows 7 into it. That way you may boot into W8, but then go direct to W7. If all goes well, later you can strip down programs not needed in W8 to make it less demanding, allowing more RAM and CPU power to W7 in the virtual system.