Thanks! Sorry for making you the guinea pig, I'm just tired/sick/scared of installing Windows 7. I had to copy the x64 dvd onto Windows 7 (32-bit) partition, and rebuild it using these obscure instructions. And then borrow my dad's NTFS external HDD and copy the resulting ISO file to it. And then reboot to OS X and burn a new Windows 7 x64 disc. And reinstall. I had this "select cd-rom boot type" error when I tried booting off the x64 disc to install, which many people said to follow those obscure instructions.
There's a simpler way of doing it.
Same procedure as described here:
http://kurtsh.spaces.live.com/blog/cns!DA410C7F7E038D!1665.entry
I've tried it and it works for Windows 7.
I used a small FAT HD partition instead
of a USB flash drive.