When restarting my computer sometimes (not all the time) my hard drive starts but I have a black screen. I then turn it off wait a while and start it up again.
Someone told me to pull the power cord out and plug it back in but yesterday it would not get rid of the black screen.
My computer is only 4 months old and I am running Vista.
Could anyone help me at all
Thank you

Not much to go on here. PC or laptop?

Does the keyboard flash a couple of times during boot, disk whirrs etc? In other words is the computer booting but you can't see what it's doing?

Quite often on PC's the monitor cable becomes dislodged and needs re-seating. And you are sure power's on at the monitor?

You see the problems of diagnosing at a distance without the fullest possible information.

We wait.

Sorry ok it's a Acer PC 512 Ram this only the PC is only 4 months old and this problem only started 4 days ago.I turn it on and it has a red light and a green light.The red light comes on and then the green light, then the red light goes off and the monitor says NO SIGNAL.
I can do this sometimes 5 or 6 times then it turns off.I rang a computer tech and he says that sometimes Acer PC's do that and I should unplug the power cord and wait a couple of minutes and then plug it back in.Sometimes this works but not all the time. The keyboard does nothing but I can still hear the drive going and a black screen.Have I got a virus or not?
Thank you for your time
Regards

btw is there any light to indicate that the monitor is getting power

Monitor displays "NO SIGNAL" = power to the monitor.

Anyway, if there is no beep and the keyboard doesn't flash like in booting, then it isn't booting.

The fact that it's turning itself off usually means a hardware fault causing the BIOS to shut the PC doen.

4 months old means warranty and this is probably your best route. I din't know which country you're in, but not taking any crap from the salesperson when you go back to your supplier can be a black art.

What you want from the supplier is:
1/
Your data streamed off and in your hands

2/
A loan PC or an immediate swap/repair configured to oroiginal delivery standard

I hope that you have all your software ti re-install.

Good luck.

Fine, you do one thing , remove the RAM out clean the RAM with Pencil Eraser smoothly and install the same again, also see that if any dirt is there in the RAM slot on the mother board. Also remove the DATA Cable and the power cable from the Hard Disk, Clean and reinstall the same, Your Problem will be solved