If you use Linux you can download a program called Wine. What it does is emulate the Windows application, so you can actually run Windows things, such as IE, Outlook, and so on.
Some friends and I have been testing Wine to see how well it functions with today's games. So far we have been able to susccesfully, and stably, run Counter Strike, Counter Strike Condition Zero, Counter Strike Source, Half Life Source, Battlefield 2, Battlefield 2 Special Forces, Command & Conquer Generals, and we're hoping to successfully get F.E.A.R to run as well. This goes to show that no matter what the target OS is, you can always get the application to run via emulation!
But back to the RAM topic.
The more RAM a program can utilize the better. The more it doesn't have to directly process is the key. The more the program can store in memory is better, that way it can access it later, while the processor processes your current data. It's like moving something for instance. Say you had to pack all of your things up, and get them to your other house as soon as you could. Well, say you only had two trucks, both being the large U-hauls. you can only store so many things into the U-Haul at once. Therefore, the more trips it will take with two U-Hauls as opossed to how many it would take with 10 U-Hauls. Get the idea? If not that's OK. But essentially it's how much you can process in the quickest amoutn of time.
The more data you can store, the better, that way you can process it later. In relation to our U-Haul example, the processing would be unloading the U-Haul. So the more you can store in the U-Haul (The RAM) the more it can be sent to the other house and unpacked (the CPU processing the data). I hope that makes sense.