This may be old news for some. After doing the system seems to run quieter & smoother
I was told this the other day & have tried it. It works fine on the 40Gb model only.
Turn off the PS3 on the rocker switch on the back, then press & hold the eject button on the front of the PS3 & turn the PS3 on again with the rocker switch. It will perform a fan test that will blow all the carp out of the machine.
Warning: Not for the feint hearted as it will sound like a 747 taking off (or a xbox 360 running normally)
This does not invalid warantee's or cause damage to your PS3, I have been told that it is the 1st thing repair shops do when you get read errors (as dust build up is normally the main cause)