dvds and my pc... feedback needed asap

i have a celeron (ya i no it sucks but i got it for free so i wont complain...) 533MHz... 400MB SDRAM winXP Pro and a dvd rom.. the dvdrom is on a channel all its own so i no thats not the problem. but what ends up happening is that in all of the new dvds like LotR and Spider Man, even a couple of times in the matrix... the movie skips... ive narrowed it down to two solutions... 1. get a new processor simply b/c celerons suck (and if this should work then do they make p3's in either slot 1 or socket 370 formfactors?)....or 2. totally rebuild my entire pc... im also running an intel 810 integrated video card... so that could also b the prob cuz ive heard those suck also.. but id obviously prefer the first of the two options because it costs less and i dont have much to begin with.. but if ne1 has any ideas...let me know