I consider this a motherboard issue, and sometimes it is not fixable. Certain boards with the AMD 64 processor socket are just trouble. In our experience, this Nv4 disp.dll error with the blue screen is nearly always an error with the nVidia drivers or the nVidia video graphics card. What is your video graphics setup?
The error is usually seen with the AMD 64 CPU, and can sometimes easily fixed by changing to an ATI video graphics card. It is also typica with the 7800 GT and GTX dards on a computer with AMD. Don't ask me why, but that is where I see it. But if you need to do this, you just need a new board.
The first part of the procedure is to find a different driver for your video graphics, or to remove/disable the one you have... and reinstall it... which is called updating by some. But using a more recent driver sometimes causes trouble, whereas an older driver will work.
The problem will not go away, in our experience, until you do a cold boot and reformat of the hard drive, then carefully, methodically, reinstall the drivers for the motherboard or computer, starting with the Chipset drivers (there may be as few as one or as many as four), then install everything else in turn, following the install instructions EXACTLY. Your problem will give you some trouble while you are trying to do this... because you need it running normally even while installing the drivers.
In reality, newer drivers do not work, so go back to an earlier driver, which you should still find on the website... or with a gurgle search
The problem is complicated by SP-3, and by Windows Updates, so you might want to survey your windows update files that are listed on your computer. And remove the ones that are suspect. You can easily see them all using Belarc Advisor. which you can print out.
Check also your device manager for red or yellow flags as you go along.
If the install gives you trouble, do ALL the install in SAFE MODE
If the NVidia drivers give you trouble, try the Omega drivers from
www.omegadrivers.net, or google for other drivers. BUT AVOID THE FORCEWARE DRIVERS.
You can also find useful information for some fix by doing a gurgle search for Blue Screen errors.
What ever else you do, be sure you REMOVE the old drivers in DEVICE Manager, after you download the new ones, but before you install them. If you absolutely cannot remove the old ones, then "DISABLE" them.
Other possibilities are present if you have one of the motherboards with the defective or failing capacitors... Look at all the little barrell-like devices that stick up about an inch from the motherboard... there can be as few as three or as many as twelve, depending on the board. Look for those with puffy tops, bulging sides, or a rust brown or grey black powder leaking from them. They can be fixed by a person good with a soldering iron, but for most people, replacing the motherboard is the common fix.
Short answer. Replace the board. This is easier than dealing with the issues that keep cropping up. Not so short: replace the nvidia with an ATI video graphics.
