If you mean using a machine running 32-bit Win7 to create a USB installation for 64-bit Win7, the answer is that it is possible. I personally install from DVDs, not USB, so I can't help you there.
The motherboard should support 64-bit OSes.
Burning a DVD from the .iso file should create a bootable DVD. Copying the .iso file to the DVD will not create a bootable DVD; did you do that?
Also, can you try the DVD that you burned in some other, known-to-function computer and verify whether or not it is bootable there?