I know it's a drag, but pretend that "Cannot install 64 but would like to"
is a little too cryptic for anyone who can't actually see what's happening
on your computer from where they're sitting. That'll help us answer your
question so much better.
IIRC if you're running 32 bit Windows on this machine at the moment your
choices are limited to a clean install or setting up a dual boot config.
Could this be your situation, and you're trying to run an upgrade?