There needs to be more detail. Blank as in it went black? Blue? was it still "illuminated" or did it just go off like it had no power? What were you doing when it happened? (I dread the answer), etc.

Also... Make/model, OS, age....

Give this a try:

Unplug the power, remove the battery and then hold the power button for 30 to 60 seconds. Then reattach the power and attempt a boot. If it works, put the battery in.

This should work if it's a static electricity build-up.

If not, There's more!

Blank as in no screen at all, black. All I hear is the fan running. Laptop is Compaq Presario CQ62. Three gigs memory, AMD cpu @2.6ghz. HDD is 320 gigs and OS is Win 7 64 bit. Its only a year old.

Tried your suggestion Doc, no go. All I did was shut it down normally and when I went to restart later on it did this.

Can you hook it to an external monitor? Could be the display died.

OK- To find out if the following may be the causes of the blank screen and follow the procedures to try to resolve each problem:

Adjust the Screen

Is it possible that someone meddled with your laptop's screen adjustment when you were away? Your computer might be set to low contrast or brightness leaving a blank screen. Adjust the laptop screen to its full range of contrast and brightness or a setting where you can make out easily the fonts. Note that a brighter screen will drain more energy from the battery.

Clear the CMOS

The CMOS, or complementary metal-oxide semiconductor, refers to a battery powered chip on the motherboard. It is responsible for retaining system information like date and time, among others when the computer system is turned off.

The best way to clear the CMOS is to read your laptop's manual and see instructions on how to clear the stored settings. Clearing the CMOS varies between laptop computers. Just type your laptop's model in Google and add a "+" sign then type "clear the CMOS". You should be able to see instructions on how to clear the CMOS of your laptop model.

If this information is not available, you may try the following procedure ***(but don't do this if your laptop has a warranty)*** to clear your laptop's CMOS:

Type your laptop's model in Google and find "how to disassemble the keyboard" instructions or download a manual for your specific laptop model (i.e., if you have lost your manual) to gain access to the motherboard. The motherboard is usually located just under the keyboard. Look for and remove the CMOS battery, that round, shiny (usually lithium) battery in your motherboard, and mount it back again after 8 to 15 hours. This is the time required for the battery to reset. You will get the message "BIOS checksum error" if you have succeeded in clearing the CMOS upon booting up your laptop. In many computer systems, the default settings are loaded once you switch power on your laptop.

Check if the Video Card is Damaged

A blank screen may also be due to a damaged video card (usually by heat). To test whether your laptop has a damaged video card, attach a video cable from your laptop to another monitor. Power on your laptop and see if the connected monitor works.

This is where you need the help of a professional computer technician to remove the video card and replace it with a new one. Due to cramped space inside the laptop, the video card may have heated up and got damaged due to heat build up. Avoid putting your laptop on for long hours to prevent this problem. If you need to spend more time using your laptop, a USB cooling fan can help put the temperature down. Also, working in an air-conditioned room will allow you to use your laptop more without the risk of overheating.

Fix Screen Cable

Using your laptop's manual, you can gain access to the cable that attaches the laptop computer's screen to the mainboard. Just be careful in doing so and make sure that your laptop is no longer covered by warranty. Remove the cable, inspect it for some damage and replace back firmly.

If you do not have a manual, the screws that hold the laptop's screen together are usually covered with either a rounded patch or a plastic plug.

How are you powering up, on battery or AC power? 

Do you get the same blank screen powering up with both? 

If yes then might it be a power supply problem?

Can you open in Safe Mode or doesn't it get that far (boot or logon screen)?

Get the same thing on both. Power light comes on and there's a blue light on the caps lock button that flashes on and off. Never did that before. Unfortunately right now I don't have the proper tool to get inside the laptop, tiny Phillips screwdriver of all things. And I'm not sure about the warranty. I don't know if its one or two years as I don't have the receipt. The person who bought it does and she's unavailable.

As for safe mode...nope. I don't even get the boot screen where it says starting windows.

If you can try Wizard's suggestion with an external monitor, that will at least eliminate a monitor problem.

Then move on to Doc's suggestions.  I would hold off opening anything unless you can verify the warranty.

I just tried using an external monitor. Same thing, no video at all. Could be the video card is toast. If that's the case its gonna be some time before I'm back up and running. I just can't afford to fix it right now. And I'm pretty sure the warranty is expired.

How many times?

I counted up to twenty and it just keeps on going.

The AC adapter light and all other lights are on?

Yes they are.

#1 Sleep or cold?

#2 you looked at it?

#3 I enjoyed that one, thanks.... 

#1- Cold.

#2- Opened up the case, removed the memory sticks and reseated them.

#3- I thought it worth a shot.

Try one thing before I tell you what you should have done to check memory.

Cold boot holding down Fn key and Power button. Look for any lights (other then the CAP) that blink. If you find one, repeat boots until you can get blinks count (short, long, etc). 

Did that and no other lights blink, only the one on the caps lock button. I did notice that the power light where the cord is plugged into the laptop stays red for a while before turning blue.

I assume you tried this, but.........does this thing boot on battery?

It does but not now. Never had any issues booting up on battery or A/C.

A bad AC adapter could have drained the battery....we'll get back to that.

As to the memory:

Alternately pull each stick and attempt boot with one stick utilizing each slot.

As an aside:

Just out of curiosity, how did you manage that 2.6 on a 320?