This question has been asked a few hundred times so far

The vast majority of software out on the market is 32 bit and should run fine on a 64 bit machine...

Most 32 bit machines will use and see up to 3.5 gigs of ram.....Depending on what you do with the machine - the majority of people can get by fine on less then 4 gigs of ram. If you're a typical user - having 12 gigs of ram could easily be a waste of money.