I have an older Pentium II macihne and I was just having a look inside the case and I did not see any brass standoffs for the case and motherboard, how did this work?
Dell did this with alot of their cases. Instead of standoffs, the areas that the mounting screws threaded into were dimpled out of the case a bit, and that allowed enough clearance between the back of the mobo and the case.
Assuming that's what your seeing, it's normal.