I'm surprised this still gets asked. Anyway, Microsoft changed the display options a while back to show total installed RAM, even if it can't all be addressed.
To make a long story short, you won't be able to use all of the memory unless you make the switch. Now, I've heard people complain about not having the time to do a fresh install, and that always means they aren't prepared or aren't properly organized. I keep a flash drive handy with Office, updated drivers, and necessary software on it. I also haven't installed Windows from a CD/DVD since XP, so that's one more way of speeding up the process. There isn't much of a need to insanely customize a computer anymore, especially for Internet settings. You should be behind a router than doesn't require much in the way of settings. If you plan ahead, you can get the entire fresh install process down to an hour and a half or so.