If you have set everything correctly and are hitting a key to boot from a DVD, I would suspect your Install Media. Where did you get it, and if you burned it yourself, you might try again and possibly even re-download it.
Alright, so I tried it instead with a 32-bit disk and it works. I'm puzzled though because I've had win7-64 bit on this computer before (i just lost the CD).
i've burned a few 64 bit cds from my university website but none of them work. i'll see if I can find a USB big enough.
I checked the iso hash and it was correct, so i don't know what's going on. I used the slowest speed for this last disk.