@onkeldave83:
yes this is all right, but ich hav a 32mb graficcard and 4gb ram!
the rest of my chips not over 900mb!
therefore openbsd should shows me 3.8 or 3.9 gb ram, but it shows me only 3!
As already discussed, you haven't allowed for chipset, cpu and i/o device requirements for memory addresses. This is explained in more detail in the references I posted in an earlier reply.
Summary: If you want much more than 3GB RAM you have to use the 64-bit OS. Your system should be able to boot it and install it to hard drive.