oh ok then.. there are 32bit applications and 64bit application. there are less 64bit applications. (not sure y) and 34bit apps only work on a 32bit OS and vise versa. so if ur used to dealing with the 64bit apps then go for 64bit Vista but id go with 32bit vista, cuz SP1 is gonna solve the issue with the RAM showing up and will show all 4 gigs