Back to the original post - have you installed the Service Pack and even more important "according to the install instructions" - without more detail on exactly your situation it is difficult to give advice in case it is of more hindrance than help.
Reading your last post it certainly seems - with the specs of your PC - to be either an install problem or incorrect use of the software.
I build routes in 04 (cause I can find stuff easier) but run them in 06 (cause it looks and runs better).
Two very good questions. Let's see if there are 2 believable answers...