Recently, my monitor has been 'turning black' after leaving it alone for a couple of hours without anyone using it.  I can still see the pointer and use the mouse, but nothing happens as I click around on the dark screen.  The only way to get it back on is to turn the whole computer off and re-start it.  I can't even do a soft boot.  Could it be I need a new monitor (it came with my  Dell dimension4700 bought in ~2003)?  I'm RUNNING Windows XP. 
Thanks in advance for any help 
When you power off the computer and re-start, do you power on the monitor again?
No, I haven't been powering the monitor again.  It just comes on automatically.  When the screen turns black I can see the power button as still green color and not amber.What happens if you hit a key on your keyboard...anything?Not sure but worth a try: right-click on an empty spot on the desktop>Properties>Screensaver>'Turn Off Monitor'>Set to never and OK out.

Let us know if that helps.

EDIT: right-click on an empty spot on the desktop>Properties>Screensaver>POWER>'Turn Off Monitor'>Set to never and OK out.

Edited to correct path.Nothing happens when I hit any key on the keyboard.  And, I already have the 'Turn off Monitor' set to 'never'. 
It's been almost 2 hours since I last used the computer and the screen is still on...we'll see how long it lasts.Just for kicks and giggles...what do you have your Power settings configured to?

Start/Control Panel/Power OptionsAnother option - Turn off the computer and monitor; remove the monitor data cable from the computer; re-install the cable and tighten screws; repeat at the monitor end, if not hardwired.

Turn on monitor and computer; I guess then you need to wait to see if it blanks out again.

While monitor and computer are on, gently flex monitor data cable at all points; slide cable between fingers; does monitor output change?

Cycle the monitor on/off with its power button.

Here are my Power settings-
Power scheme:  Always on
Turn off monitor:  Never
Turn off hard disk:  Never
System standby:  Never
Sytem Hibernates:  Never
Hibernate:  Enable hibernation (selected)

I haven't tried disconnecting the cable yet.  That's next.  Will let you know.
Can you test this monitor on another computer? If you cannot continue to read. One simple way to determine if it's just the monitor going out or the computer crashing is to play some audio on your computer. Perhaps load up a very long mp3 play list, for example. If the monitor goes black, but the music continues to play, you know that the computer is running, and that the problem is either the video card, video drivers, the monitor or the cables in between.