cablegaai it seems you don't have an opencl platform (or you don't have the driver), so of course it won't mine.
I get it now, you actually have to download the ATI SDK soft and install it! Someone just could have told me, and all the others who are having the same problem.
The error msg wasn't really clear when i started guiminer.exe since it said i didn't had to take care of it when i would mine on CPU.
So for all the newbies out here like me install the ATI SDK
You can find it here: http://bitcoinminer.com/post/3828447301/ati-stream-sdk-downloads