I have two gigs of RAM in my HTPC, running Win7 64-bit. I like to listen to an online streaming radio station, and about every week or so, the page turns into an icon with an exclaimation mark, the flash plugin ate all the free memory up or something. Then I have to restart flash. So if you leave any programs running, like streaming media, and use Flash, then I would put in 4GB to be safe.