A ram upgrade will help you out loads. The cpu is kinda on the slow side if you are using windows xp but its still very useable if you just use the laptop for the net and email n stuff.
You could reduce the quality of the appearance of xp (im afraid I cant tell you how because I dont use xp) ie the pretty blue bits! This would surely speed up windows explorer and the start menu.
I think its the theme. Change it to classic by right clicking on the desktop and go to properties.
Run the defrag tool too. It makes all the difference on our slow pc.