Hey. I have a compaq Presario F500. I was on it just before, until around 6pm, then i put it into 'sleep' mode. Usaully this is fine and all i have to do is lift the screen up and the laptop wakes up. This time that didnt happen. I lifted the screen up, the fans started going, light started flashing (as usaul) and the screen was showing nothing. I held the power down, laptop turned off, then i pushed it to start it up. Again, the fan started going (for about 3-5 seconds), the lights flashed (as it usaully does when i turn it on) and then after 15-20 seconds it turns itself off and then back on again to repeat the process. In this entire process i dont see anything on the screen. Just lights flashing and fans going.
I have tried: Turning it on with the battery and Main Power running through it.                 Turning it on just with the battery                 Turning it on with just the main power.             
No matter what way i do it it just doesnt work. I usaully have it plugged in with the battery and main power. This has happened before and i used to be able turn it on with no battery in - not this time though.
All information is helpful.
Cheers