I have purchased Minecraft and am trying to play the the download version, but I get the following error:
[failed to get system properties (java.lang.NullPointerException)]

org.lwjgl.LWJGLException: Pixel format not accelerated
    at org.lwjgl.opengl.WindowsPeerInfo.nChoosePixelFormat(Native Method)
    ....

It works fine when I run it in the browser. I only get this if I run the downloaded version, even the minecraft.jar version of the GUI (and who's bright idea was it to name the GUI jar the same as the game jar?!?!). Why does the browser version work and the download version not work?

I have downloaded the latest video drivers from Intel using their auto detect tool. I have downloaded the latest version of DirectX and tested it. Hardware Acceleration is turned to maximum. I can play WoW on this (admittedly old) computer, why not Minecraft?

My kid wants to use the Wolves Extended mod, but apparently you have to replace some of the class files in the Jar, so you have to remove the META-INF folder in the jar file to get rid of the MD5 hashes, which makes the browser version think you are hacking and only does the free version. Is it possible to load a mod in the browser version?