whenever there is'nt much space left on my pc , wich doesnt happens a lot but well, i use this http://download.cnet.com/WinDirStat/3000-2248_4-10614593.html?tag=mncol;1
it shows in cubes what are the biggest files, so you can see directly the big ones and see if you need them... now i must say, if you're planing on keeping this lapotp you could always buy a new hard disk, they're very cheap. and also notice, if you're hard drive is more then 50%full, you're pc or lapotp wil slow down. but wel, try windirstat, and that will free up some space , and you could also do the windows things, like clean up c/ but i don't now where that is anymore, xp was a long time ago for me . . .