HP Compaq Presario SR1738NX will turn on, but nothing besides the fans seem to work

When I start the computer here is what happens:

1. The fans immediately start and the green lights on the 2 dvd/cd drives flash on then off
2. Keyboard lights flash on then off. Keyboard lights won't go on with num lock or caps lock.
3. Power light at bottom front is amber.  It flickers every so often.
4. Monitor does nothing.
5. Fans sound louder than usual (although I could be imagining that)
6. Green light in the back stays lit
7. After this, if press the power button for several seconds, it stops for an instant then starts up again. The only way to turn it off at that point is to unplug power cord.
8. I tried a different monitor, just in case that's all it was, but it didn't work.

I realize this is an old computer, but I can't afford an new one at this time, so any suggestions are greatly appreciated!!