I think the transition from 4gb to 8gb memory being the average standard is upon us soon. When running Battlefield 3 and Skype, my machine uses around 4Gigs of memory - and my OS is stripped down (configured msconfig, services etc.).
or if you want to upgrade to 8gb but want to use 32bit verson then read this trick to address extra 4gb ram
www.tomshardware.com/reviews/ram-memory-upgrade,2778-4.html