Specific reason analysis:
In general, when an error occurs by the system boot record, the system boot record is in the logical 0 sector and is generated by the Advanced Format command format. Check that the main boot partition table is correct, according to the system partition indicated in the partition of the starting address, read system boot record, if read failed, show "Error loading operating system" errors, if you can correctly read the system boot record, The primary bootstrapper checks to see if the last two bytes of the system boot record are 55AA, and if this is not the two bytes, a prompt for "Missing operation system" is given. This problem can only be repaired with NDD, and the steps are as follows.
1, the first to Win7 system repartition, is estimated to be 0 track error, because 0 track can do the guide, 255 track can also do guidance, it must be in the partition of the first extended partition or hidden partition, the main partition in the final;
2, then the system to start the necessary three files: Msdos.sys,io.sys and Command.com, you can use the system Recovery disk into the command Prompt window, copy into the system disk, and then type the following command.
Copy MSDOS. SYS C:
Copy IO. SYS C:
Copy Command.com C
3, if not successful, had to use the format c:/s command to rewrite the DOS boot record. If the problem persists, it can be solved by reloading the system.