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This might be a silly/ simple question but I wasn't sure of my knowledge on the matter so I wanted to ask people with (hopefully) better understanding :)

Consider the following situation: you have a computer that's a couple of years old connected to an instrument. Is it possible to just take out the HDD and put it in another (newer) machine and boot as before?

My initial response to this question, when I was asked yesterday, was "no, since the MBR will most likely not recognize the new hdd,and not know what to boot/where to boot from". Could anyone confirm or deny this? Furthermore I would really like if you could elaborate a bit on the details on what goes on between the rest of the hardware (lets say the motherboard), the MBR and the HDD, when a machine powers up.

Thanks!

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Please add what Operating system you are using (I assume Windows) as that will affect the answer –  Tog Jun 8 '11 at 8:36
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See also: Removing HD from PC and putting in another PC and all the answers below –  slhck Jun 8 '11 at 9:12
    
@Tog: I was trying to generalize as much as I could, since I was interested in the theory rather than trying to solve a particular problem. In the case which I was asked both machines run Win7. @slhck: Thnx for the link, I'll be checking out the answers to that question as well. It seems like that the drivers are the major problem in a HDD swap –  posdef Jun 8 '11 at 10:05

2 Answers 2

up vote 2 down vote accepted

When the machine is booting, it firstly call the BIOS.

Provided the BIOS recognises your HDD, it will call the MBR which is located on the HDD (it's not a special device or component). Each disk has a MBR. Each MBR is setup to direct the computer to read specific area of its disk to enable booting of an Operating System.

So provided there is no compatibility issue with your HDD and hardware, the computer shall be able to boot your disk. To finish with, you also have to hope that your operating system will "like" the new hardware. Since older OS tends to install driver at first installation, you may end up with problem in the execution of your OS which will be trying to find its old hardware. Try to use safe mode booting of your OS to troubleshoot.

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Ah of course, it makes sense... Why should the MBR be on anywhere else than the disk itself.. :$ embarrassing confusion on my behalf. Thanks for pointing it out, and for your answer in general. Regarding the compatibility issues, what exactly do you have in mind? Is there much else to worry about other than the connection type IDE/SATA/SCSI etc? –  posdef Jun 8 '11 at 10:08
    
I'm not a hardware guy, but it could happen that your motherboard does not support your disk. On the software side you can have a lot to worry about: Video driver, disk driver, keyboard driver (if it changed from PS/2 to USB for example). If the OS is recent enough, it will fetch the drivers as the peripherals are recognised and it should be ok. But if it's an older one... who knows. –  M'vy Jun 8 '11 at 10:36

The MBR isn't the issue. Leaving aside things that install themselves as MBR computer viruses, such as GRUB, proper conventional MBRs have little to be affected by differences between machines. The principal thing that varies from machine to machine that affects how the bootstrap code in MBRs operate is the presence of the Phoenix/IBM/Microsoft INT 13h extensions. Some MBR bootstrap programs simply assume that the extensions are always present. Its absence isn't really a concern for machines manufactured in this century, since most retail PC firmwares shipped since the middle to late 1990s have these extensions, so your concerns about the MBR are largely a red herring.

The more appropriate focus of concern is addressed in the answer to the question that was pointed out by shlck above. The device drivers employed by your operating system, as configured and installed in a system volume on the disc, may be completely wrong for the new machine.

For Windows NT, for example, the HAL and the "boot start" class drivers must be the right ones to enable the system to come up on the new hardware. (This is the Windows NT version 6.x boot process.) Microsoft already provides Microsoft KnowledgeBase article #249694 detailing many of the factors that will stop this from being the case; so I won't repeat them here.

The same concerns apply to other operating systems. For Linux, as another example, Carla Schroder notes that you can be faced with "typically cryptic and unhelpful" error messages if the compiled kernel being bootstrapped and (as M. Schroder doesn't explicitly state but as Andryan Prakasa Gouw notes) all of the initrd modules don't properly match the new hardware.

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