I love urban myths, but I get a secret grin when I tell people some things that I know to be facts and they dismiss them as Urban Myths or me pulling their leg!
My first example is the hard disk in the freezer trick! If your PC won't boot up and you reckon this is down to a hard disk drive failure then if all things fail I suggest taking the drive out and wrapping it up in cling film or a sealed freezer bag (must be air tight) and then leaving it in the freezer for an hour. The most common cause of HDD failure is component seizure and rapid cooling can unstick a stuck drive. However the problem is very likely to recur so this only gives you about 15-30 mins of cold life during which you should back up everything you can from that disk.
My second example is very much a last resort and will only work for a self acknowledged geek. We all know that in Voodoo rituals you often require the blood of a freshly sacrificed chicken, but given that techno geeks tend to steer clear of anything fresh or bloody, I can confirm that waving frozen chicken portions over a dead PC, three times clockwise and three times anti-clockwise gives a true believer the ability to reboot a stalled system!
If you do find the two tricks above don't work for you all I can say is that (a) the hard disk is REALLY fucked or (b) your faith / geekiness is not true enough.