If you had a system that was setup like this:
- partition C: only 'Windows' folder + boot files
- partition D: only for folders 'Program Files', 'Program Files (x86)' and 'PortableApps'
- partition E: only for folders 'Users', 'ProgramData' and your own personalized folder structure for your user data if you such a system
In that case it is relatively easy by dumping the registry keys from the installed software in Win7 32bit, install the customized 64 bit version of Win7 (here is a
link on how to do that), import the earlier created registry dump and that should be it.
If this is sound too complicated, invest time in looking for portable versions of the software you like/need/desire. I have done that while on my XP installation. When the time to upgrade was forced upon me, 80% of the software I use regularly was immediately available/use-able. All-in-all it took me 2 hours to convert from XP Pro to Win7 64-bit, mainly because I was reading through all the installation options from the Win7 installation DVD.
EDIT:
See this
thread and this
thread for software that can make portable versions from normally installed software. That should make migrating easier.