Monitor not recieving input

I have a Dell Dimension 8200 Pentium 4 with Windows XP. I set my computer to standby like i do every night, and this morning I tried to turn it on. Everything turned on normally except the monitor stayed with the yellow light instead of going green. just a blank screen. The keyboard still worked.

I read somewhere to disconnect power and hold ON button for 30 seconds. it didn't work. I read somewhere to remove the CMOS battery to reset BIOS. (then put it back in). That didn't work either. Now the keyboard lights up when turning on but doesn't communicate with the computer past that.

I hear no POST code when I boot up.

Help?