How can I reset to the factory settings?
Bricking a device usually refers to getting the ROM into a corrupted state, by flashing with a bad ROM or a failed flash. As Pi has no ROM, you can't brick it like that. Pi runs off the SD card only, so a clean reflash of the SD card should fix it.
If a particuar card is not working (and has never worked) there is a list of known problem cards on a wiki: http://elinux.org/RPi_VerifiedPeripherals#Problem_SD_Cards