256mb of ram is absolutely crap and hopeless and 512mb of ram will barely make a difference so if i were you i would go for at least 2gigabytes of ram.
Unplug the computer pull it away form all the cords and wirer. Lay it on a flat and soft area such as a bed. Use a screw driver and unscrew the one screw on the back to your left. Look in the back...
You would upgrade RAM if you wanted to improve the performance of your computer when it runs desktop applications and web browsers. If your computer is running fine when you are running applications...