I have had a decent pc with a ATI Radeon HD5970 2GB GDDR5 that I have had for roughly 18months. On the weekend, I reformatted my pc, and took apart / cleaned my mobo, and case. For the mobo, I just got rid of alot of dust, debri, etc. Also I took the graphics card off my mobo, and most specifically cleaned the graphic card fan.
Ever since I did these few things above, my graphics card sounds like a 747 jet engine anytime I play a video game(BF3) or play any sort of video.
Before I reformatted and cleaned my case/motherboard, the graphics card never sounded like this ever.
Dont just clean the fan but also get some compressed air to blow out the heatsink as.well.
Dl msi afterburner to check temps amd also get a custom fan profile to help keep them down more
Once your.temps are noted then adjust accordingly
If they stay high beyond reason then maybe a reset with thermal compound is in.order
If it is running too hot, re-apply thermal paste to both of the gpu's on the board. This should lower temps and also lower fan noise, however if it is just the fan speed and not the temperatures set a custom fan profile in MSI Afterburner.