Help...HP Pavilion a340n won't start up...black screen

Good evening,
Thank you for taking the time to read this.

Last night, I turned my computer on, checked my email, and shut down the computer like I do every night. I didn't even go on the net.

Tonight when I started it up, the power light came on, the hard drive lit up solid for about 5 seconds, then went out. I never even saw the HP screen or anything, just a black screen.
Then my monitor lost the signal and went into power saving mode.
I tried it again, same thing.
I ensured that there is no floppy or CD in the drives
I unplugged the computer from the wall for 60 seconds.
I unplugged all peripherals except the power and the monitor.
Nothing has worked. Still get nothing when I start it up.
I can hear the Harddrive run for the first 5 or 10 seconds, then the light goes out, and nothing else happens.

Any ideas?

Thanks so much