1.) If the RAM is bad, the system can not POST.
2.) Like, stuck in the memory count? Bad RAM maybe? Or maybe it's being run above its rated speed.
3.) Some PC's can boot without a videocard, some won't. My 8RDA+ board won't POST unless there's a videocard AND monitor attached, but I've used some older boards that'll post and boot to Windows with no videocard in the system.