OK, I'll bite. This is very confusing at best. If you have XP (like me) it is very clear what is the minimum. However, if you are running Vista or Windows 7, it does look as though you require the 64bit version.
I keep reading the heading - it says 'minimum', and then the line below which says 'Windows Vista/Windows 7 (64bit)'.
How from those two bits of information would you draw the conclusion that 32bit is OK for Vista or Windows 7?