4Gb RAM and Vista 32bit pagefile

With 2gb RAM and Vista Ultimate on my PC, I found that (unlike XP) several hundred mb would be written to my pagefile (2 pagefiles on 2 drives) especially after exiting a demanding program or game. I measured this with Doug Knox's XP Page File monitor program. I recently added another 2gb RAM to my PC a 4gb total. Well the PF activity has been reduced considerably but still I would see up to 4070mb on each PF after about an hour of PC usage or a playing a demanding game. This in contrast to XP where the peak PF acivity would be no more than 3 or 4 mb after heavy usage or a tough game. Why is that? I would have thought that 4gb RAM would eliminate any PF activity.