7gigs is 7168MB
to stop system restore using up valuable drive space click: 'start/control panel/system/system restore' then click 'settings' and reduce the ammount of space it takes up on your drive.
3-4% on my 80gig + 40gig drives gives me a few weeks worth of restore points to choose from. depends on size of your drive. i find this doesnt slow the computer at all.