You will need to do a clean install on the 64bit hardware. I’m actually amazed that it’s worked this long with all the different drivers.
The 32bit OS is going to be totally different than the 64bit OS. Not to mention you’ll need to reinstall all your software anyway with 64bit editions of it (Office, etc).
In order to be able to have most of your settings on the new install I suggest you to use the Migration Wizard (start/run/migwiz.exe and press ENTER); this will giude you in exporting your data and settings that can be later be imported on the new install.