Dual Booting

RichDRichD Essex, UK
edited January 2010 in Science & Tech
This may seem like an odd question but here we go. If you have a dual boot system you get a little menu that asks you which OS you want to load. Where abouts does that menu sit? It cant be part of the OS as niether OS has loaded and you haven't chosen which one you want to load. If I only have one OS installed there must be somewhere something that tells the PC where to look for the OS. Can anyone offer any help as to how this happens?

Thanks

Rich

Comments

  • kryystkryyst Ontario, Canada
    edited January 2010
    Depends on which two OS's you are trying to dual boot between. If it's linux and windows then the Grub boot loader exists in the master boot record, which is something windows doesn't really use. For practical purposes it's only accessible from linux.

    If it's between two different versions of windows xp or older then there is a file called boot.ini that creates the list. Windows now with windows 7 (and I think Vista) have changed that yet again and there is a boot directory that controlls things but I haven't looked into it enough to know how it really works yet.
  • RichDRichD Essex, UK
    edited January 2010
    But how does the system know whether to look at the boot grub or boot.ini. Doest the bios just keep looking til it finds one?
  • kryystkryyst Ontario, Canada
    edited January 2010
    If there is something in the boot sector (grub) it will get loaded before anything in boot.ini. It's just the order of events when a harddrive is accessed. So yes it's a function of bios.

    You could have information in both. For example you could have a grub menu that pops up and sayd do you want to boot windows or linux. If you pick windows then the boot.ini kicks in and if you have alternate choices there it'll prompt you to make a choice.
  • RichDRichD Essex, UK
    edited January 2010
    I see. Presumably then that would be why I needed to flash my bios when I first bought Vista as the boot information was stored in a different place to where the Bios was expecting?

    Can you edit boot.ini?
  • _k_k P-Town, Texas Icrontian
    edited January 2010
    Yes.
  • kryystkryyst Ontario, Canada
    edited January 2010
    I just looked it up Windows Vista no longer uses Boot.ini either. It uses a new boot loader called Boot Manager it can be edited through a program called bcdedit. But read up on it here.
  • RichDRichD Essex, UK
    edited January 2010
    Cool. Thanks for the info guys.
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