A method for copying data from a source hard drive to a target hard drive is implemented in an electronic device. The source hard drive stores a master boot record (MBR) recording a SYSTEM partition and at least one other partition. The electronic device copies information related to the SYSTEM partition to a file to store in the source hard drive and modifies the MBR to be a modified MBR by erasing the SYSTEM partition. The electronic device then creates a diagnostic sub-partition for system diagnostics in one of the at least one other partition, copies the file to the diagnostic sub-partition, and copies the modified MBR in the target hard drive. When the system diagnostics is implemented for the target hard drive, the electronic device restores the SYSTEM partition in the target hard drive based on the file.