HELP! Can't get windows or anything!

Last night, my computer crashed, froze, and then nothing would load up.

Now the monitor won't even detect anything there. The keyboard isn't being detected. The mouse is though. But nothing is on the screen. The fans will run, but nothing else will.

I tried putting in a new graphics card, and HP said it could be the motherboard. But I don't want to buy a motherboard, if that's not the issue. But I'm not sure what else it could be!!! It's so frustrating, I had to bring out my old computer to get online.

Additional Info:
I removed the Ram. No beeps. I took out the battery, and put it back in, no beeps. Argh!

If you can't get anything to display, then you're limited to swapping parts until you stumble on what's causing the problem.

Disconnect all the parts that you absolutely don't need (CD/DVD drive, add-on cards plugged into the mobo, anything plugged into the case).

Then, start unplugging what's left, looking for some sort of display. Unplug the hard drive and see if it shows anything on the screen. Try another power supply. Etc, etc, etc.