Windows NT/2000 supports more memory and doesn't have that problem. Your just over the limit with 256, so that means windows has blocked 56 mb of memeory and is running as if it has only 200 mb or your upgraded from a lower amount and you don't see the slow down because of the sudden jump in memeory. Point is if you add anymore memeory you will not see a speed increase or your system will slow down.