is your hardware _old enough_ for your distribution? there should have passed some time between the building date of your pc/notebook and the release date of your software, otherwise it may not support your hardware. e.g., for my main machine which i bought in january, there is only one possible linux-distro that supports the complete hardware.
so what are you trying to set up, which hardware and which distro do you want to use?
there are many possible things that can lead to a desktop-refusal such as wrong configuration of your screen, not supported graphical environment or lacking permissions. and thats not all, of course. so further information would be helpful.
ps the brave must win--and the brave is red!