How do I install 64bit from 32bit?

How do I install a 64 bit OS using my OEM Recovery installation DVD I initially created after I unboxed my laptop? I initially chose 32 bit by accident, but now I want the 64 bit OS.
I have an HP Compaq 6715b Vista Business. I tried to follow your tutorial, but I don't have an option to delete my partition and create a new one. I also don't have the option to choose 32bit or 64bit. I had the option to choose 32bit or 64bit on the initial install when I unboxed it and set it up. Please help. Thanks.
:D
Jimmy

Hello Jimmy, and welcome to Vista Forums.

The tutorial is for doing a clean install with retail Vista installation media instead. What you would be doing is considered a factory recovery of Vista on your HP computer instead.

I haven't seen where you could select between 32-bit or 64-bit before, but you might see if the link below may help.

HP and Compaq Desktop PCs - Performing an HP System Recovery (Windows Vista) - c00814731 - HP Business Support Center