A good way I tell people to see if they need more RAM is to watch how active the hard drive is. Not always the best method, but when you don't have enough RAM, your system uses a swap file, ore basically a portion of your hard drive as RAM. Your hard drive is MUCH slower than RAM, so this really slows a computer down.
Yes my hard drive goes like crazy when loading games and stuff.
Thats why i need more ram and i have 512mb of ram at the moment so i would hate to immagine whats its like with you having 256Mb mate.
I say definatly get more ram.