afterburner (that happens with an 1 bit brain):
- a 64-bits os can't be installed on a 32-bit system (afaik).
- you can however install a 32-bit os on a 64-bit computer. it will work as a 32-bit system though.
this way 32-bit software which is not ported to 64-bit, can still be used.
- a 64-bit system supports more memory (32-bits goes up to 3GB).
- a dual boot may be a nice way to test both.
a nice article i found is http://www.tomsguide.com/us/64bit-win7-upgrade,review-1496.html