I got a Dell laptop with XP and pent 4, and i've found, not so much on DVD's, but on other media, i can only watch movies for 10-20 minutes before they become unsync'ed. I think it's heating up too much, but even with a fan it does it.

Any advice?

I often find my movies going out of sync. To rectify this I usually stop what I'm playing and select the scene I was in and play it again. This usually works.

Only other thing I can suggest is trying a different player or updating your codecs

i had that problem on my old computer, i think its to do with ram, that or a scrath on the DVD

Thor has pretty much got the jist of what I think it will be down to, simply the codec is causing the loss of sync. As I've mentioned in other threads when you watch a Divx or DVD the file that you use has two or more layers of data encoded into it, these layers have like the picture and sound in.

Now the pictures are in one compression format and the sound in another, and there is the encoding thats stuck these two layers together to try to keep them in sync. Depending on what codec you are using (and if it's newer than others) means that you might on occasion see your system struggle with either the sound or the pictures (or both) and you'll start to see the loss in syncronousy.

What you can try to do to defeat the problem is:
Update the program you are using to watch media (This will fix programming flaws in the program)
Update (or load new) codecs that your media player use's

If it still fails just try another media player, it's programming might be better for that codec type.

Sounds like a memory leak.

I have the problem on windows.

Under linux, it never happens :)