With a 32-bit operating system, the maximum amount of addressable system ram is 4,096 Kilobytes (4 Gigs). If you put 4 Gigs of RAM into a 32-bit Vista PC, this is what you'll see under your system stats. There are hundreds of explanations for this in as many different levels of tech-speak. However, to put it in layman's terms--a 32-bit operating system can only address up to 4096 Kilobytes of memory. That sounds fine in theory, because that is the amount you have installed right? Well, this is where things get a bit more complicated. 32-bit operating systems develop a 'memory hole' and for those who have been around long enough, think back to the 286 days when we were using DOS commands with the XMS managers to try and put device drivers into extended memory, above the 1024 mark. Remember that 'hole' that resided between 640 and 1024 that we couldn't put anything into? Same basic principle applies here as Windows is trying to stash all of our device drivers into memory, addresses are quickly being eaten. The end result, the hole. Yes, there are various hacks that have been developed by at-home programmers to help 32-bit Windows desktops overcome this issue, but unless all of your applications are coded to work with these third-party modifications, then they won't be able to utilize the extra memory properly. Face it - it's time for the 32-bit operating system to just -- go away.