MBR for bootmgr clarification

#1
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
 

mqudsi

Mostly Harmless
Staff member
#2
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.