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Can Bios Limitation Prevent Windows From Booting If No Boot Flag Set?


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#1 caljohnsmith

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Posted 05 September 2008 - 08:41 PM

I know from experience that I can boot Windows on my machine even if its partition doesn't have its boot flag set by using a boot loader like Grub, and this is also the experience of most of my friends. But I have one friend who claims he must have the boot flag set on his Windows partition or he can't boot it, even with a boot loader like Grub that doesn't require having the boot flag set to boot a partition. He claims it is a limitation of his BIOS; I don't understand the logic behind that, because I thought that once BIOS hands the boot process over to the master boot record (MBR), then BIOS doesn't care whether any partition has its boot flag set, only the MBR might. For non-configurable boot loaders like the Win XP MBR, the Win MBR relies on one of the partitions having the boot flag set, because that is how the Win XP MBR decides which partition to boot. But that is not the case with Grub, as Grub can happily boot a partition regardless of whether it is the active partition (i.e. has its boot flag set on). Or at least that has been my experience.

So does anyone think that BIOS could somehow be stopping Grub from booting his Windows partition just because it is not the active partition? Because that is not the experience of myself or most of my friends. Thanks in advance for any help.

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#2 hamluis

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Posted 06 September 2008 - 08:21 AM

I believe you're wrong in your assumption about the active partition, unless I've misunderstood what I've read. The Grub code defines its own active partition and is not dependent on the MBR for such definition (which may be exactly what you said, but I misinterpreted).

http://www.dedoimedo.com/computers/grub.html#mozTocId616834

Of course, there's always the possibility that Grub has become damaged on the system in question.

This answer to your question seems to say what I'm trying to say, http://www.linuxquestions.org/questions/li...lag-set-667877/

Louis




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