>Under 64-bit Windows a 32-bit installer will use 32-bit registry only. If installer is 32/64 architecture aware, it'll install 64-bit application and use 64-bit registry. The 32-bit applications cannot see 64-bit registry and vice versa.

I sense a nice trap... you have a 32-bit component, which automatically updates and goes 64 bit behind the scenes... and all of a sudden an app somewhere stops working because the 32-bit version was uninstalled, and it can't see the new one.

Perhaps a worst-case scenario, and I guess the devil doesn't need an advocate. This will happen somewhere.