Just boot up any Linux Live CD and activate Grub in root console.
If Centro is in say hda3 you can tell Grub the root of Cento is in the 3rd partition of the 1st disk by (hd0,2) and set up its Grub in the MBR.
You will find Grub back after a reboot.
Remember Grub counts from 0 and (hd0) is the whole disk meaning the destination is the MBR.
If you are not sure which partition Cento resides then issue at the root console command
It should be the first partition with type No. 83 in your case.