Leonard03: Edit: no luck at all.
It wouldn't. Your MBR is fine as is your
grub.cfg. You can safely ignore the "Unknown BootLoader on sda2" warning as nothing is attempting to boot from sda2, your extended partition. Though I'm curious if a NTFS partition used to start there. Anyway your boot problem happens
after GRUB/Windows boot code reaches the NTFS partition.
The "Error loading operating system" is a XP specific error that commonly happens when the geometry of the NTFS partition is wrong. Which might have happened when one resized the partition. I didn't actually check, but I assume this is the case for you. Hex edit the correct values in or copy off all the files to sdb, delete the partition, recreate the partition, format the partition and copy the files back. Ideally do the recreate & format steps from Windows install/recovery media.