Why would a person buy Windows 7 64 bit?

I have been flocked with PC problems relating to this software. My computer freezes at least 6 times per day, so does my bosses. Both PC’s crash when playing flash videos. I’m starting to think that I should have bought 32 bit instead of 64 bit. Is there any truth to someone telling me that 64 bit is intended for computers that dual boot or have 2 motherboards (something like a server)? Something that divides it in to 32 bit? I would also like to know the difference between 64 bit and 32 bit.