its just started happening i have got bright yellow stripes down my monitor, about a inch to half a inch apart.
do i need to replace the monitor? ive tried degausing. could the problem be the video card.It could be either one.  Have you DONE anything to the PC lately?  Changed or moved graphics card, monitor or cables?  Noticed any STRANGE smells?

Personally I WOULD suspect the graphics card since you're getting something on the monitor.  Check your monitor on another PC if you can.

Delli havent changed anything lately, but i have bought this PC from MESH and the computer has had continuos problems. the ting is even at the screen of windows xp at the start up the line going across becomes more than one line, it goes into 2 PARTS, then the screen has black strips all the way down and will not start up. the monitor seems to be fine at the moment but usually in about 20mins the yellow stripes will appear againDoes this happen while in the bios and in safemodeno it does not happen in the bios. my friend definately thinks the graphics card might be a bit stuffed.
today I got this message: The ATI Control Panel failed to initialize because no ATI DRIVER is installed, or ATI driver is not working properly. The ATI control panel will now exit. Go to Control Panel/System/Hardware/Device Manager and un-install the video card.
DLoad the latest video drivers for that card and have them nearby for your next re-boot.
If you are lucky it is just corrupted drivers and that card is fine...

patio.  Yes sounds like a driver issue to me. Or a fault on the graphics card.