07-11-2007
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Re: BOOTSECT.BAK
On Tue, 10 Jul 2007 11:50:00 -0700, xeriouxi
>Well if I've formatted the whole drive etc. then the previous XP stuff
>shouldn't be there, should it? Hence nothing to make a backup of...
Oh, OK; I think I see what you mean.
My guess is that Bootsect.bak is a copy of whatever was in the PBR
(Partition Boot Record, or more accurately in this context, just the
first sector of this) at the time that etc.
Firstly, there will always be something in that sector, whether it be
zeros or disk-probe "divide-by sign" characters. The install process
that creates the .BAK can't know whether these contents matter, so it
prolly makes the backup irrespective of what was there.
Secondly, while PBR is part of the OS, it may not be wiped by a Format
(in fact, the Format will most likely re-create it) and it may also be
(provisionally) created by partitioning tools even without a format.
Win9x used to do the same thing, tho the file was called something
else. Virus scanners would sometimes "catch" boot code malware in
there, where the Win9x install has backed up such code into the file
before splatting down the OS's new boot code.
PBR boot code is very OS-specific, and differs between Win9x (where
IO.SYS is the first file to load) and NT (where NTLDR is the first
file to load, and may be on NTFS).
So in the context of installing an NT OS over (or as an upgrade to) an
existing Win9x, it's necessary to back up whatever PBR was there.
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