First of all, YES i'm careful. I'm using This Guide to increase performance using all kind of options. The link brings you to the overclocking page. I'm using the ATI Tray Tools program. First to just check some options to increase performance, but now i'm using it to overclock my card. I'm using a RADEON 9600/9800 PRO by the way (There is no program which can recognise which one it is AFAIK, they all say 9600/9800 pro, and I don't know either) and my graphics card is 128 MB. And I got 2.66 GHZ whatever it's called, and 768 MB ram.

Well the thing is, when I use the benchmarking I saw my "score" decrease every time I increased the core speed. My score was higher when I lowered it under the normal (263) number. I don't know exactly what this score means, but it also gives a comparison with other cards. The better cards had a higher score. So a high score is a positive thing.

So why does my score gets lower when overclocking, and gets higher when "underclocking" ?

Edit: When I raised it a bit further (307) than I did the first times , I suddenly doubled my score. I had around 1900. Then I lowered it to 302. My new score? 3900 (what the?) passing the average X800 PRO with 2.5 Ghz. Was this just luck or something?

Edit 2: It seems this test isn't really good. I tried the test twice on 300 mhz. The first time i got 1947, the second time 975.

So I guess that it was a coincidence that the number was lower when I "underclocked" it.
Alright, a new question: Is there a good free program to overclock with, or to test it with so you know when you've reached your limit?

you've reached the limit if you're starting to get graphic errors. usual the core "underclocks" itself if the temperature gets to high, so you don't realy have to be worried about overheating^^

whatever: if you don't know EXACTLY what you're doing: ask a (RL)friend to show you how to overclock. I've learnd it from a friend of mine too and it's realy the best way to learn such things^^.