Okay .

We can all agree that 2GB of RAM would work wonders, especially with the latest types of OS. 3GB might be even better; but with RTW, or M2TW for that matter, it's highly unlikely you'll ever need it if you use the program conservatively. (That is, you just play and don't mod it extensively - in a modder's case you may want to run both the game and other applications at the same time which is seriously demanding.)

Also, if you just have been doing something demanding in terms of RAM, you may want to spend a while on the Internet (just load up the explorer - don't start actually browsing the web or something). By starting up a new, light program, you tell your OS to get rid of all the junk previously stored in the RAM - without putting as much/more different junk there. Hence, nearly all of your RAM will be available immediately to your demanding application; which will decrease start-up time.

Now you may wonder what other programs can be so demanding in terms of RAM that you have to do this. Well, there's all kinds of Office for example. Copy/paste a lot, and behold the custom lag you can create!