Doug recently replaced a power supply, and now the computer won't boot up to his main hard drive. Leo says that the SATA cables may have been swapped and that can confuse the BIOS. He should disconnect the data drive and see if it boots to the boot drive. If it doesn't, he can swap out the cables. He should also clear the configuration data in the BIOS so that it can reset. There's also a possibility that his boot drive is damaged, so he should check that. Getting rid of the master boot record on his data drive will prevent confusion as well.
Penny has an old tower computer that she wants to get rid of. Leo suggests keeping the hard drive and donating the rest of the PC. She tried to boot it up to move the data off the hard drive, but it won't boot. Leo suggests that she check her keyboard connection. Sometimes a computer won't boot if a keyboard isn't properly connected. The BIOS battery or motherboard battery could have died. The hard drive may have gotten stuck. It's called "stiction." Penny should try taking out the hard drive and putting it into an external enclosure to see if she can still read the data.