I'm creating a Windows desktop application and want to include a database. I've chosen SQL Server Compact 4 but when I download it there are two versions (32-bit and 64-bit). My development machine is 64-bit, so do I download this version? Or, do I download the version that I expect users to run (which, I guess, is most likely to be 32-bit). If I download and work with the 64-bit, when I release the database, will it cause errors on 32-bit machines? Thank you.
If you distribute your application with scripts to build the database (not a database backup or something like that), then in theory it should make no difference which version (of 32-bit and 64-bit) you develop against. Back when 64-bit was new and shiny (which was SQL Server 2000), there were some advanced features that 64-bit didn't support, but in 2005/2008 they should be functionally identical.
(Not that it should matter if you're using Compact Edition, but there are some configuration differences between 32-bit and 64-bit once you get to the point where your DB performance is an issue.)