Cleaning your video card every now and then is not a bad idea.

XFX HD 5770 1GB (Radeon HD 5770 is the same.)

What you need

1. A small "Philips: PH 0 – 3 x 40 screwdriver

2. New thermal past

3. Alcohol to clean the GPU and cooler from the old thermal past.

Loose the 4 screws round the GPU.

This will loose the complete fan and holder. No need to loose other screws, they are for the RAM cooling.

GPU diode temp before cleaning was 82°C, after cleaning 55°C almost 30°C difference. And that makes a big difference in noise of the fan.

Now my card is clean and silent again :)