Well, if this sound is coming from a power supply that is too weak, invest in a power supply with higher wattages. Or this sound may just be from a power supply that is just on the fritz.
You can't really help it from happening in the future, but what you can do, is buy a good make, which will obviously last you much longer, and be more stable than a really cheap one.
Look for one that has a good 12v supply to the rails, and is as stable as possible, and one that has at least 450-500watts I'd think.
yea i don't think any less is acceptable anymore really all the new technology is bumpin ^ the eletric bill i asked my dad "what would u think if i got the 1kilowatt power supply?" and he said "no" lol
yea true, i did notice that my 6800 GS pulls alot of power because my psu has fans that only activate when a good bit of power is being pulled meaning more heat is being produced and the fans are activating alot eairlier than they used 2 lol. maybe if i turn down the fan!... lol not really