Damn HIS cards and their crap fans. They always seem to die.
I'm assuming the fan is either dead or dying. So here's what I'd do if I were you
1. Remove the cooler from the card. It's basically all of the Philips screws on the back. The center 4 are the ones that actually hold the cooler to the GPU. Be sure to use the right size screwdriver. If you strip those little screws you'll have a really hard time finding replacements as most hardware stores do not carry ones that small. I believe the screwdriver you'll need is a Philips#00.
Once the screws are removed, unplug the fan from the card and see how it's attached. Probably another 3 screws from the backside of the plastic shroud. Remove the fan.
On the back of the fan, there'll be a bunch of numbers. You can use these numbers to buy a replacement fan off of eBay. I did that with a 5870 I had (also a HIS card). It came all the way from China so it took a little bit, but it worked perfectly. While I was waiting, I took the shroud(the plastic part) off of the cooler and zip-tied a 120mm case fan to it.
Once you get the fan out, take a picture of the sticker on the backside and post it up.
Also, you can try to dismantle the fan. It's only held in by a retention ring. If you use two wide flat bladed screwdrivers, you can pop it off usually. Then smear some Vaseline on the shaft and reassemble.
You can use silicone lubricant too. However, it's best if it's a grease of some sort.