Portal 2 and a better computer

So I want to get Portal 2, the problem is that I have insufficient funds and I have a computer that may not support the game. It can run the first Portal but it lags a bit, when I record with fraps, it will lag like hell. I heard that I may get a better one, which is a desktop and I currently have a laptop. I may get it in a week or two, but I am not sure... or I may not get that at all. I think the desktop may cost like a thousand, that may be another reason it may not be bought.