usually its 2 ram slots, so if you got 256 in one, you can add whatever you want to the second (actually using similar size on both slots is recommended)
there are some ways to optimize the use of ressources (google for optimize windows recording producing), but if youre running on 256 or even less id suggest to get new ram. i had the same problem, tried every possible way of tweaking the system, but windows itself needs too much memory.
now i have 768, everything works well, but i wouldnt suggest less, especially if you like to use real time effects or if you record tracks with your pc.