I remember a friend who bought an MSI P965 along with a new 550W PSU.
He didnt screw in the brass mounts on the backplate for the motherboard to sit on and just screwed it in.
Firstly when he powered the mobo there was a spark and that was the onboard sound shot to bits. He didnt realise at the time but once windows was installed, it wasnt even finding it under new hardware when he enabled the onboard sound in the bios.
Secondly, once he had done the fresh install he switched the pc off to put it all in the case, powered it back on, the psu went bang and the mobo was completely mullered. He did an RMA and said it was D.O.A and the shop replaced it.
He then found after reading through step by step instructions on the web how to install a mobo that he had not put the brass looking mounts onto the backplate before screwing in the mobo.
The shop actually called him a few days later as they had tested the mobo he sent back and they said that he was very lucky to get another one as what he had done, did not fall under the T&C of a replacement as they advised it was miss-use