MBR for bootmgr clarification

I had 32XP/64XP/32Vista/Ubuntu working but it broke!

I need a mental map to repair this - I have two 40GB drives with similar setups
and one works still and the one I'm trying to repair looks "OK" (clearly it isn't)
but I lost a dependency and can't figure what I need to do to repair. I'm trying
to make sure I know how to get the mechanisms right as fallback before I split
these into two co-operating drives with (say) 2 OS each and either re-bootable in case of fail.

Right, given just 1 drive...
My model says the MBR is not in a partition (in this setup) and it is GRUBby
so it heads off to the Linux partition /boot/grub/... and pulls up the menu.lst
and that lets me chain off to Windows land in partition 1 (that's my XP32 partition).
Well, at that level of abstraction both my disks are OK.
Now, on the working disk, I had set up Vista and EasyBCD so that partition 1 is augmented with bootmgr.
So, when I shoot off to (hda,0) from grub/menu.lst I get the Vista menu that lets me drop
down to ntldr+boot.ini
On the otherhand, on the disk I'm trying to fix up
- and it appears to have bootmgr in partition 1 too -
it goes straight to the ntldr+boot.ini menu
...and that's what I'm trying to put right.

I realised I hadn't really appreciated (or have forgotten) what grub is doing
when it goes to partition 1; how does it know to pick up ntldr or bootmgr ?
My guess is that there's a sort of MBR parked at the front of Partition 1
and it's either Vista or pre-Vista;
then if Vista, BCD or EasyBCD maintains the portal down to pre-Vista ntldr.

If that's the case, which way do I fix this ?
a. via EasyBCD ...as it just replaces the in-partition "MBR" of partition 1
b. do I risk Vista repair destroying my non-partition MBR
.. if (b), does grub setup take the MBR Vista sets up and then park it at the front of Partition 1 ?

...will either way work
Thanks, Mark


Mostly Harmless
Staff member
Hi Mark,

I'm sorry, but I'm not sure what you're trying to accomplish exactly (as in, which OS is it that won't boot?).

GRUB doesn't actually know whether to load BOOTMGR or NTLDR - it loads the bootsector of the partition you specified, which contains code that in-turn loads either BOOTMGR or NTLDR depending on the version of the bootsector that was loaded.