post beep

I have a dell optiplex GN,p200,32mb, win95. Not always but at least 60% of the time when I turn on my pc or reboot I am getting a series of beeps 2 long beeps then 4 short in a row. The hard drive is running and no signal to the monitor. I have on board video. I unplugged everything out of the back and took out all cards, reseated the memory and tried. Still got the beep. When I get it to start up I tried to press cltr + alt+ enter to go into the bios and the screen goes black with a curser flashing. I sometimes have trouble restarting. It will just hang on the shutting down windows screen. Does anyone know a link where I can get info on these beep codes? Any suggestions on my problem….