fsck: Boot sector backup… What backup?

 Disk /dev/sdc: 8075 MB, 8075120640 bytes
249 heads, 62 sectors/track, 1021 cylinders
Units = cylinders of 15438 * 512 = 7904256 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x2c6b7369
This doesn't look like a partition table
Probably you selected the wrong device.
   Device Boot      Start         End      Blocks   Id  System
/dev/sdc1   ?      125407      245362   925929529+  68  Unknown
Partition 1 does not end on cylinder boundary.
/dev/sdc2   ?       86163      121076   269488144   79  Unknown
Partition 2 does not end on cylinder boundary.
/dev/sdc3   ?       34914      125493   699181456   53  OnTrack DM6 Aux3
Partition 3 does not end on cylinder boundary.
/dev/sdc4   ?       90338       90339       10668+  49  Unknown
Partition 4 does not end on cylinder boundary.
Partition table entries are not in disk order
dhcppc0:/home/homunculus # dd if=/dev/zero of=/dev/sdc
dhcppc0:/home/homunculus # dd if=/dev/zero of=/dev/sdc bs=446 count=1
1+0 records in
1+0 records out
446 bytes (446 B) copied, 0.00957615 s, 46.6 kB/s
dhcppc0:/home/homunculus # dd if=/dev/zero of=/dev/sdc bs=512 count=1                                                               
1+0 records in                                                                                                                          
1+0 records out
512 bytes (512 B) copied, 0.000639452 s, 801 kB/s
dhcppc0:/home/homunculus # dd if=/dev/zero of=/dev/sdb bs=512 count=1                                                                   
1+0 records in                                                                                                    
1+0 records out   
512 bytes (512 B) copied, 5.2413e-05 s, 9.8 MB/s                                                                                        
dhcppc0:/home/homunculus #
                                                       
Source

$ sudo dosfsck -ar /dev/sdc
dosfsck 2.11, 12 Mar 2005, FAT32, LFN
There are differences between boot sector and its backup.
Differences: (offset:original/backup)
  90:33/8c, 91:c9/c8, 93:d1/d0, 95:f4/ff, 97:8e/fb, 98:c1/8e, 99:8e/d8
  , 100:d9/8e, 101:bd/c0, 102:00/fc, 103:7c/bf, 104:88/20, 105:4e/00
............
............
  , 485:74/39, 486:0d/39, 487:0a/00, 505:ac/00, 506:bf/00, 507:cc/00
1) Copy original to backup
2) Copy backup to original
3) No action
? 1
/:7zH:7hP:4uQ:5AX
  Bad file name.
1) Drop file
2) Rename file
3) Auto-rename

http://www.linuxjournal.com/article/8366