Most likely correct. Check to see if the Fan is still spinning properly. If not, it will likely need replaced, which may not be easy and may require you to buy a complete Heatsink/Fan for GPUs. If it is really dirty, a cleaning might solve your issue. Given the age and Artifacting/Heat, there is a strong chance that the card has permanent damage though.
Do those GTX 460 cards even work with modern titles? They aren't supported by modern NV drivers, that's for sure. (Fermi)
A card that old, if you haven't been cleaning the dust and hair and grime yearly at least, and re-pasting it every 3 years or so, is probably dead/dying from heat-death. Happened to a friend of mine, he never cleaned out his PC/video card, until his PC was crashing and blue-screening, by then, it was too late for the card.