i purchased a new biostar socket 939 mobo. it has been working fine. i try to put a stick of pqi 512 ddr40 in my mobo and i go to turn it on and the pc freezes after post scan. i had 1 gig of ddr400 prior. and when i took the pqi out the pc still froze after the post scan.
That's unlikely. More likely is that you did something to it while changing the RAM. For example, did you remember to unplug the PS, etc, before starting? With luck, the problem may be reversible -- try clearing the CMOS memory first.