Display corruption.... HELP!!!

I have a DELL Dimension 4600 with an ATI Radeon 9800 Pro 128MB graphics card, which has been in there since new (about 3 years ago). In the last few months I've started getting display corruption in the form of vertical strips of randomly colored pixelation, with other random dots/patches of pixelation on the rest of the screen (see attached image). I'm pretty sure it's a heat problem, but I don't really know. It's worse in high graphics demand programs, such as games, and it's is worse if I use the digital output as opposed to the analogue output, and gets worse the longer the PC is turned on. I've looked at the power lead to the card and it doesn't seem toasted, but the card produces color changes in the pixelation. I don't really want to fork out a wad of cash for a new card if I don't have to, but I have to do something soon before I can't see at all!! Please help while I can still see your replies!!!!!!!!
Thank you!!

 

Welcome to the forum jimThe symptoms you decribe and the screenshot look like the card is on the way out,first inspect the card to see if the fan is spinning,check to see if your case fans are spinning,if you have installed any extra hardware recently check the cables arnt restricting airflow through the case remove the card and give it a good clean make sure all the fins are clear of dust also make sure the rest of your computer is clear of dust with some canned air

Next right click your desktop and go into your video card properties to check the temperature of the card,depending on the model and installed cooling you want the temp to be under roughly 50-60c,if it isnt and the fan is spinning touch the heatsink to see if its warm to the touch,if not you'll have to remove the heatsink and apply some TIM

If it isnt a temperature problem next try reinstalling the driver download the latest from ATI,remove using add\remove programs and then run a driver cleaner,use ATI catalyst cleaner or this and reinstall the latest driver

http://majorgeeks.com/Driver_Cleaner_Professional_d3214.html

le me know how it goes