Personally I would do a few things if I had this problem.
1. Reapply the thermal paste on the GPU - I've done this to every card I've ever owned and it lowers normal temps up to 5c for a really good application/thermal paste. If this was your problem (old GPUs thermal paste dries out from getting hot then cold over and over again) you will see huge gains like 35c at idle and 65c under load.
2. Make sure your power supply has the intake on the outside. Some people accidentally install it so that it pulls air from inside the case and blows it out. This is actually counter-intuitive. Instead of sucking hot air out of the case and making the case cooler, it actually warms up the PSU, causing it to run hotter, less efficiently, AND causes it to radiate more heat into the case. Having the intake fan on the outside of the case lets it pull cooler air into itself and then eject that warm air directly out of the back without adding it to the case.
3. Uninstall any GPU tweaking software. You make have set a setting too high or fiddled with something you shouldn't have (like playing with voltages on an old card... BAD idea) or it is conflicting with something else.
4. Do a complete uninstall of your graphics driver and all it's saved preferences and options. Then find the most recent driver off the manufacturer's website. This seems like too easy a fix to work, but trust me.... it's worked before.
5. Assess the airflow in your case and the placement of your PC in the room. Every case needs at least one intake and one exhaust fan. Without some form of fresh cooler air, your PC will always run hot. I would place an intake on the front of the case (side with the power button and CD drives) at the bottom aiming at the GPU. This will give it fresh air and force the warm air up (warm air naturally rises and cold air will displace it further.) Then I would put the exhaust fan on the back of the case (where the motherboard sticks out and connects to stuff) so that the warm air from the CPU and rest of the case gets sucked out. As far as PC placement in a room, make sure your PC is at least 5 inches away from clutter or large objects that could obstruct or trap air (please oh please don't stick it in a cabinet or under a desk) and if your PC has feet, see if there is at least 1cm or a half inch of space off the surface it rests.
Follow all of these steps and I guarantee there will be at least some improvement to your temps.
Edit - Spelling and stuff.
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