My laptop specs:

512 mb of RAM, out of which 64 mb are shared with an integrated GPU - ATI Radeon Xpress 200 M. Intel 1,6 Ghz Celeron M single-core processor.

I've spent months trying to figure out why compositing and effects sometimes lag on any distro I try. Now I've come to realise that no matter what drivers I try (the default ones work for me on pretty much any linux) compositing lag is random.

When I used Ubuntu 10.10, for example, sometimes window compositing would lag and sometimes it wouldn't. The PC is able to render those effects so hardware is not the problem.

It's completely random and unpredictable - sometimes when I turn on the computer the effects lag horribly and sometimes it's completely smooth. I've also checked startup items and there doesn't seem to be any unnecessary entries.

I also tried building my own OS with Arch Linux and the problem persists there, therefore I can only assume that it's a driver issue of some sort.

By default there are lots of drivers supplied with linux distributions. Could it be that they're in the way? The ones that I need are ati/radeon (or both? What's the difference between them?) and there seem to be a lot of others... What should I do?