Blank Monitor Screen? Please Help

I have a Blank Monitor Screen on my Computer.
First off it is an Older Computer
Comapaq Presario S4020WM
With a On board Graphics Card.
I have one and my Daughter has an identical Computer we bought at the same time. So I've been double checking everything on her computer and mine.
I've tried several Remedys for this. Suggested by others. and the official Compaq site.
I've checked the Monitor. It's working fine.
I've checked the Connections to the Computer. They are not loose and seem fine.
I replaced the IDE Cables to the Hard Drive.
I checked my Hard Drive in My Daughters Computer. And It's working fine.
I put in Brand new Memory. Which I checked on My Daughters Computer and it's working,
My Computer Boots up fine As far as I can Hear... But all I get is a Blank Screen so I can't see anything.
Does anyone have any suggestions??

 

The onboard graphics card may have died....if you have an AGP or PCIe slot that will allow you to plug in a separate graphics card, you could test this....

 

That's a pretty good report

Since you have successfully checked the memory without damaging it and the hard drive runs I can deduce the following. The psu is OK and the Power_Good signal is present allowing the motherboard and psu to start.

Lack of video can be due to four other causes. Listed in ease of checking not probability.

1) Nearly flat coin cell battery on motherboard, scrambling bios settings.

2) Dead graphics circuitry.
Switch the monitor in first, through an auxiliary lead if needed.
Power up and watch the light (not cursor) on the monitor. It will change
colour or from flashing to steady if the monitor receives a valid video
signal.
Use Lev's method to confirm, PCI or even ISA is preferable.

3) Shorted bus on motherboard or by dead card.
Remove all cards and try boot again.

4) Dead processor.
Swop with your daughter's, paying attention to any speed jumpers on
the motherboard.

let us know how you get on and good luck

Studio T