Why does chainloader complain “invalid signature”?

My computer has multiple harddisks and every disk has multiple partitions. I install the SLES (Suse Linux Enterprise Server) on the 5thpartition of the 2nd harddisk, but find it can’t boot:

grub> set root="(hd1,msdos5)"
grub> chainloader +1
error: invalid signature.

After checking installation steps, I find by default, the SLES can’t install bootcode on the partition:

1

Click the install option in the above picture, then it will install the bootcode :

2

then the boot process is OK!