"I can say: No, it isn't possible. Why? The adress violation begins at the BIOS and the CPU directly. Windows can only use what the CPU and BIOS make available. And coLinux can't have more rights then the windows kernel ..."

This is not quite right. XP prof 32bit is detecting and using maximum of 4gb ram. The most common misconception is that only 3GB can be used. Actually, the upper limit is around 3.5GB, for usermode. Single app is maxxed out at 2GB. What happens with the remaining memory? I could roughly explain it, but better read this article, done by Mark Russinovich: http://blogs.technet.com/markrussinovich/archive/2008/07/21/3092070.aspx