I just upgraded my gfx card to a geforce 8400 and my PSU to a 400 Watt. Now when i power on my CPU, everything turns on but i don't get signal to my monitor. My cpu beeped three times when i first turned it on but then stopped after that. I don't know if its a motherboard issue or what. My CPU is a HP A6400F and my PSU is a dynex 400 watt power supply. My new GFX card is a galaxy geforce 8400 gs. Any ideas?
Yes, that's right.
That's CMOS battery.You can try reset it, take it out for about 5-10 minutes and plug it back.
For beeps sound, make sure all the cables are properly connected, including 4pin for cpu and 8+4 pin for motherboard.
or you can try re-seat the RAM.