Automatic Boot Disk redirector?

Whenever an external drive is plugged into my PC, the BIOS gets all
confused and it rearranges the boot order of the drives. You then have
to go into the BIOS setup and rearrange them back, which is a temporary
solution until you don't connect external drive and you have to do it
all over again. Or use the BIOS's boot device chooser which is even more
temporary.

What I'd like to know is if there is some kind of automatic boot sector
manager that can be put onto non-boot disks and redirect the boot
towards the right disk?

Yousuf Khan

In comp.sys.ibm.pc.hardware.storage Yousuf Khan <> wrote:
> Whenever an external drive is plugged into my PC, the BIOS gets all
> confused and it rearranges the boot order of the drives. You then have
> to go into the BIOS setup and rearrange them back, which is a temporary
> solution until you don't connect external drive and you have to do it
> all over again. Or use the BIOS's boot device chooser which is even more
> temporary.

> What I'd like to know is if there is some kind of automatic boot sector
> manager that can be put onto non-boot disks and redirect the boot
> towards the right disk?

> Yousuf Khan

In theory, a bootable disk has a boot-signature in the
boot-sector, while a non-bootable disk does not have it and
should be skipped. As soon as the boot-secotr is loaded into
RAM and executed, it is actually too late as the BIOS has
relinquished control to it permenently at this time.

A PC bios expexts 0x55 0xAA in the last two bytes of the
first sector of a device in order to consider it bootable.
Maybe just overwriting these two bytes with 0x00 0x00 would
do the trick, but maybe it could confuse other software.
It should be easily reversible though in case of problems.

Arno
--
Arno Wagner, Dr. sc. techn., Dipl. Inform., CISSP -- Email:
GnuPG: ID: 1E25338F FP: 0C30 5782 9D93 F785 E79C 0296 797F 6B50 1E25 338F
----
Cuddly UI's are the manifestation of wishful thinking. -- Dylan Evans

On 1/16/2012 8:40 AM, Arno wrote:
> In theory, a bootable disk has a boot-signature in the
> boot-sector, while a non-bootable disk does not have it and
> should be skipped. As soon as the boot-secotr is loaded into
> RAM and executed, it is actually too late as the BIOS has
> relinquished control to it permenently at this time.
>
> A PC bios expexts 0x55 0xAA in the last two bytes of the
> first sector of a device in order to consider it bootable.
> Maybe just overwriting these two bytes with 0x00 0x00 would
> do the trick, but maybe it could confuse other software.
> It should be easily reversible though in case of problems.
>
> Arno

Does this have anything to do with "active" and "non-active" partitions?
Because I have already tried removing the active property from any
partitions that had active set in them. It didn't do anything though.

Yousuf Khan

Yousuf Khan wrote:
> Whenever an external drive is plugged into my PC, the BIOS gets all
> confused and it rearranges the boot order of the drives. You then have
> to go into the BIOS setup and rearrange them back, which is a temporary
> solution until you don't connect external drive and you have to do it
> all over again. Or use the BIOS's boot device chooser which is even more
> temporary.
>
> What I'd like to know is if there is some kind of automatic boot sector
> manager that can be put onto non-boot disks and redirect the boot
> towards the right disk?
>
> Yousuf Khan

Does your PC have a popup boot menu ?

On my Asus motherboard, you press F8 early in POST. On the Asrock, it's F11.
There will be a list of drives presented, and you select the one you want.
The selection is temporary, and if on the next boot you don't press any
key, the preference in the BIOS is applied. The popup boot menu selection
is not recorded. The mechanism avoids the need to enter the BIOS and make
changes and save them.

That can function as a workaround, when the BIOS messes things up
when new disks are added.

Paul

Hi, Yousuf.

> I have already tried removing the active property from any partitions that
> had active set in them

This may be a big part of your problem. In order to boot from a disk, it
must have exactly ONE "active" partition. To be marked active ("bootable"),
that must be a primary partition, not a logical drive in an extended
partition.

RC
--
R. C. White, CPA
San Marcos, TX

Microsoft Windows MVP (2002-2010)
Windows Live Mail 2011 (Build 15.4.3538.0513) in Win7 Ultimate x64 SP1


"Yousuf Khan" wrote in message news:...

On 1/16/2012 8:40 AM, Arno wrote:
> In theory, a bootable disk has a boot-signature in the
> boot-sector, while a non-bootable disk does not have it and
> should be skipped. As soon as the boot-secotr is loaded into
> RAM and executed, it is actually too late as the BIOS has
> relinquished control to it permenently at this time.
>
> A PC bios expexts 0x55 0xAA in the last two bytes of the
> first sector of a device in order to consider it bootable.
> Maybe just overwriting these two bytes with 0x00 0x00 would
> do the trick, but maybe it could confuse other software.
> It should be easily reversible though in case of problems.
>
> Arno

Does this have anything to do with "active" and "non-active" partitions?
Because I have already tried removing the active property from any
partitions that had active set in them. It didn't do anything though.

Yousuf Khan

Yousuf Khan wrote
> Arno wrote

>> In theory, a bootable disk has a boot-signature in the
>> boot-sector, while a non-bootable disk does not have it and
>> should be skipped. As soon as the boot-secotr is loaded into
>> RAM and executed, it is actually too late as the BIOS has
>> relinquished control to it permenently at this time.

>> A PC bios expexts 0x55 0xAA in the last two bytes of the
>> first sector of a device in order to consider it bootable.
>> Maybe just overwriting these two bytes with 0x00 0x00 would
>> do the trick, but maybe it could confuse other software.
>> It should be easily reversible though in case of problems.

> Does this have anything to do with "active" and "non-active" partitions?

Nope, thats a different issue entirely.

> Because I have already tried removing the active property from any partitions that had active set in them. It didn't
> do anything though.

Yeah, most bios just ignore that now when deciding what is bootable.

R. C. White wrote
> Hi, Yousuf wrote
>> Arno wrote

>> I have already tried removing the active property from any partitions that had active set in them

> This may be a big part of your problem.

Unlikely given that changing that made no difference.

> In order to boot from a disk, it must have exactly ONE "active" partition.

Hasnt been like that for a LONG time now.

> To be marked active ("bootable"), that must be a primary partition, not a logical drive in an extended partition.

But there are plenty of boot managers that can boot those too.

>> In theory, a bootable disk has a boot-signature in the
>> boot-sector, while a non-bootable disk does not have it and
>> should be skipped. As soon as the boot-secotr is loaded into
>> RAM and executed, it is actually too late as the BIOS has
>> relinquished control to it permenently at this time.

>> A PC bios expexts 0x55 0xAA in the last two bytes of the
>> first sector of a device in order to consider it bootable.
>> Maybe just overwriting these two bytes with 0x00 0x00 would
>> do the trick, but maybe it could confuse other software.
>> It should be easily reversible though in case of problems.

> Does this have anything to do with "active" and "non-active"
> partitions? Because I have already tried removing the active property
> from any partitions that had active set in them. It didn't do
> anything though.

In comp.sys.ibm.pc.hardware.storage Yousuf Khan <> wrote:
> On 1/16/2012 8:40 AM, Arno wrote:
>> In theory, a bootable disk has a boot-signature in the
>> boot-sector, while a non-bootable disk does not have it and
>> should be skipped. As soon as the boot-secotr is loaded into
>> RAM and executed, it is actually too late as the BIOS has
>> relinquished control to it permenently at this time.
>>
>> A PC bios expexts 0x55 0xAA in the last two bytes of the
>> first sector of a device in order to consider it bootable.
>> Maybe just overwriting these two bytes with 0x00 0x00 would
>> do the trick, but maybe it could confuse other software.
>> It should be easily reversible though in case of problems.
>>
>> Arno

> Does this have anything to do with "active" and "non-active" partitions?
> Because I have already tried removing the active property from any
> partitions that had active set in them. It didn't do anything though.

> Yousuf Khan

That is something else.

Arno
--
Arno Wagner, Dr. sc. techn., Dipl. Inform., CISSP -- Email:
GnuPG: ID: 1E25338F FP: 0C30 5782 9D93 F785 E79C 0296 797F 6B50 1E25 338F
----
Cuddly UI's are the manifestation of wishful thinking. -- Dylan Evans

In comp.sys.ibm.pc.hardware.storage R. C. White <> wrote:
> Hi, Yousuf.

>> I have already tried removing the active property from any partitions that
>> had active set in them

> This may be a big part of your problem. In order to boot from a disk, it
> must have exactly ONE "active" partition. To be marked active ("bootable"),
> that must be a primary partition, not a logical drive in an extended
> partition.

No. In order to boot old Windows versions it has to be like that.
But as the BIOS does not undertsnd partitions, it does not understand
whether a partition is active or not.

Arno

--
Arno Wagner, Dr. sc. techn., Dipl. Inform., CISSP -- Email:
GnuPG: ID: 1E25338F FP: 0C30 5782 9D93 F785 E79C 0296 797F 6B50 1E25 338F
----
Cuddly UI's are the manifestation of wishful thinking. -- Dylan Evans

On 16/01/2012 2:20 PM, R. C. White wrote:
> Hi, Yousuf.
>
>> I have already tried removing the active property from any partitions
>> that had active set in them
>
> This may be a big part of your problem. In order to boot from a disk, it
> must have exactly ONE "active" partition. To be marked active
> ("bootable"), that must be a primary partition, not a logical drive in
> an extended partition.
>
> RC

Well, as I said, I removed all of the partitions previously marked as
"active", and it made no difference.

It was a royal pain to do it too, because although Windows' Disk
Management can turn a partition active, but it cannot turn it
"inactive": what was Microsoft thinking, it costs too much to put the
reverse command in? Instead, I discovered that you have go to an arcane
commmand-line based tool called Diskpart to do that. The tool itself is
not so bad, I figured it out quite quickly, it was just a pain to search
through Google to find this command in the first place.

Yousuf Khan