LOL this is gonna be funny
edit: if unixmad is actually planning on having someone update this you guys better hope he doesn't wait until the last minute (lol) - converting software from 32-bit to 64-bit is a lot harder than taking it out of one container and putting it into a bigger one. There are actually specific and sometimes complex problems involved with the differences between types and type sizes from 32 to 64.
A very rough comparison is if you take a small cake out of its container and put it into a bigger one, but then realize that the cake slides around because there's more space and gets beaten up and crumbled because of that. There are some interactions between types and assumptions that can be made about certain structure sizes that are very convenient in 32-bit but don't work whatsoever in 64-bit.