I have HP Pavilon slimline s 5389D and i can't turn on my computer ,just hear sound ...beepp...beppp...and at my monitor status is not signal ( VGA and DMI ). can you help me solve this problem?

Try another monitor that you know works. If that doesn't work it may be your video card or chip.

Sounds like a component has gone bad on the computer. If you have a dedicated video card, I'd replace that first. Otherwise, it's likely the motherboard has gone bad and needs replaced. If this is the case, it's going to be just as expensive to replace the board as it would be to get a newer system.

more than likely it is set to to the wrong frequency. try and start the pc in safe mode and adjust the frequency to 60 hrtz. that should take care of it.

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very simple bring a new AGP card and plug in it on your pc and plug the monitor pin in new agp now start your computer . monitor will turned on.

if the monitor is not turned on its mean your have problem in your ram or mother board for that pluged out your all rams from your pc and start your computer if cpu ring a beep its mean you have ram problem and the mother board is ok but if you cant hear any beep its mean mother board's problem ram is ok.

If you saying "doesn't always boot", most common would be motherboard...
If your motherboard still beeps, then probably some other components has the problem like RAM, GPU card etc., depends on your motherboard.

Hope that give an idea...

Does the computer turn ON? (do you hear beeps?, do you see lights on the computer NOT THE MONITOR?, do you hear the fans?, etc...) it could be the monitor, try an other one, it could be the video card, swap it with a known good one ,it could be the VGA cable change it, etc... if the computer is all dead try an other electric outlet.

Good luck!

the problem might be coming from your video card or try changing your RAM

It sounds like your computer has been having some trouble for some time. My hunch is that there is nothing wrong with the monitor at all.

Usually, when you see this warning on the screen that there is no signal, the monitor is trying to tell you that it cannot talk to the computer. This means the computer either a.) will not boot or b.) your video card in the computer has stopped working.

Does your computer make all the usual noises when you start it up? Can you hear the hard drive clicking and the fans come on?

Have you reseated the video connection on the back of the tower?

My guess is that something was going out before and it is now gone. The first place I would look to diagnose this problem is the hard drive.

Hard drives fade to fail sometimes, and when they are fading, the entire computer becomes painfully slow.

Hope this helps
good luck
tony

Mostly it may be your memory problem. try any system checking softwares which are freely available in net. check the memory. 

try changing the video card of your computer..