You can install 64 bit over the top of 32 bit, you just must boot the DVD.
If it fails when DVD drive is set first in BIOS setup as shown in tutorial I posted, then try tapping the one-time BIOS Boot Menu key at boot.
Why do you keep telling us about command lines and error prompts that only mean you are not booting the DVD? Boot the DVD, period.
If it won't boot via either method then confirm the ISO or burn another using the ISO download for your licensed version and tools provided in Clean Reinstall - Factory OEM Windows 7