I've had my PC for about 3 years now and recently dark horizontal LINES have been appearing across the screen where the IMAGES are DARKER.  At first I THOUGHT it was a problem with the monitor so I tried hooking up my old monitor, but still got the lines.  I tried changing my refresh rate, but still have the lines.  This is REALLY starting to annoy me.  I can't even SEE images when the background is too dark.  Would really appreciate help ASAP.  Thanks in advance.I suggest you clean your videocard thoroughly (Remove dust) check the cables, replace them if necessary.

Perhaps even uninstall the videocard drivers, then take out the videocard, see if any dust or other types of unwanted visitors have settled in the slot and then place it back in.

If none of this solves the problem, you may have to look into buying a new videocard. Or try a different slot.what does dxdiag report..type it in the run  box to find out?I already tried running the dxdiag.  No problems turned up, but I'll try cleaning the video card.have you tried setting  video modes to 800x600? what operating system is this and what graphics card?