Given the age of the card it is probably broken. You can find cards of that age pretty cheap so its not a expensive replacement, such as a 750ti which is more powerful. Or you can buy something that's newer like a 1030GT
9800GT temperature is relatively high, at that time it was the flagship. Virtual welding due to high temperature is normal.
Maybe it's a hint that you're going to buy a new video card.
Now there's a way for you to use the hair dryer to turn on the hottest gear and blow the core position of the graphics card for more than ten seconds. See if you can save it.