Dodgy PSU + hoover = much quieter

I found over the last few days the psu (power supply) in my computer was getting noisier and noisier. This was normally solved by banging it with my hand. But even that had stopped working.

So today, I had finally had enough. I took the psu out and as I suspected it was chocked full of dust. I decided against taking the psu apart for fear of being electrocuted. Instead I poked out lose bits of dirt with a screwdriver. I could still see a load of lose dirt in there though. So I tried to shake it out, and then I got the hoover involved. I moved the hoover head around the holes of the psu and it sucked up a considerable amount of dirt. I then put the psu back in the system. And it is now much, much quieter.