if you have perform a clean install...
reinstall the windows 32 bt
if you are having some problems with some programs running on windows 7 64 bit
you can try running a virtualized windows 7 32 bit or any other 32 bit os
this way you can still use windows 7 64 bit and use your programs in the virtualized os
If you plan on using more than four gigs of ram then I would recommend upgrading to the 64bit version of windows. No, you can't just upgrade, however, you can save your user profile, pictures, settings, and everything else using the microsoft user state migration tool found here: (Its free)
Once you back up your data to and external drive using this tool, do a fresh install of microsoft windows 64bit. Install all your programs that you had from your old computer, then install the User State Migration Tool and select new computer to import all the settings. It sounds harder than it really is, but there is no need for the 32 bit windows anymore.