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HI,

I have a "old" system with Windows 7 installed. Now I have a new mainboard and a processor. Is there a way I can use my "old" hdd instead of reinstalling windows 7 again?

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Some people are saying it should "just work", but I'd still recommend you back up any important files (to DVD or something else) before attempting this. ;) –  FrustratedWithFormsDesigner Aug 5 '10 at 17:05

6 Answers 6

up vote 2 down vote accepted

One of the biggest problems with reusing Operating Systems is regarding drivers. I am not sure how Windows 7 will handle it, but back in the XP days (last year...) XP would oftentimes have problems with such dramatic switches in hardware as it experiences with a mainboard swap. Sometimes this might crash the computer, and sometimes XP would be able to limp through enough for a user to install a correct driver. Depends on how well the default driver handles the mainboard.

My guess being that Windows 7 contains more and newer drivers, it may be able to handle some component switches fairly competently. I say go ahead and stick the HD in, and worse comes to worst, you just reinstall windows 7 right?

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Everything went very well, no problems, just one reboot and one install of a NIC (2 onboard) –  Chris Aug 10 '10 at 20:48
    
nice to hear. thanks for updating us on the situation. –  Jonathan Aug 12 '10 at 12:45

I have done this a few times. Windows now does an absolutely amazing job of handling it compared to any other OS or past Windows version.

It has worked every time for me. But that may not be the case for you.

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Linux is far better at this than Windows. Change enough and windows will complain about activation, or often just fail to boot, and almost always needs drivers. I've had USB installed on a USB stick (full install, not live), and it's worked flawlessly on dozens of different machines. –  Dentrasi Aug 5 '10 at 19:01
    
@dentrasi - have you tried Windows 7? It almost never blows up, unless perhaps you move an AHCI installation to a machine that has it disabled. It will prompt reactivation, though (which is all of 20 seconds, usually.) –  Shinrai Aug 6 '10 at 14:29

Starting with Windows Vista, Microsoft changed that way that Windows installs itself. It now provides a generic image that is copied to the hard drive. This image will then boot and configure itself for whatever hardware it finds.

What that means for you is that the likelihood of success from the kind of thing you're proposing is now much higher than it used to be. However, there is still a good chance that this initial system has now changed enough to be incompatible with your new hardware, so I would at very least take a good backup first.

Moreover, I'm concerned about the disks themselves. Hard drives are parts that move very fast most of the time, and like any other moving part they — along with power supplies, cpu fans, and optical disks — are among the most failure-prone parts in your computer. Additionally, when a hard drive fails it takes your data and program installations with it, making them in my opinion the riskiest piece of hardware to carry over from build to build as you upgrade your system. Another consideration is that hard drives are typically the largest performance bottleneck on your computer — even more so than cpu speed or ram. If you're updating your hardware because you want a faster system, you may have missed the most important part.

Put all that together, and if these drives are very old at all I would consider them for replacement as well anyway.

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I've done this multiple times. You may need to reinstall some drivers, and if one of those drivers is for your network card it may be challenging to get new ones unless you have another PC.

Besides that it should work fine.

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I agree with what others are saying.. Try it, it's better these days, it may 'just work' and it shouldn't have an effect on your old drive if it doesn't.

Aside from that: Windows 7 has system image backup and restore capabilities built-in; which should allow you to back it up to an external target on the old hardware, and then recover the image to the new hardware.

From my understanding (haven't personally had to do it to 'different' HW yet) it works like the old ASR backup of previous Windows' NTBackup in that it will retain the new drivers fed to the 'new hardware' during and after the restore (the 'official' MS way to move Windows to new hardware back in the day was via this method).

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I have done this. My main computer had an Asus board and a dual core processor. I decided I wanted to use that system as my TV computer and I built a new gaming computer with a gigabyte board and quad core processor. I took the hard drive out of my main computer (it dual boots Ubuntu and Windows 7) and put it in the new one. None of the hardware was the same. Windows recognized that more than the allowed number of components had changed and they made me reactivate my license over the phone. The internet would not work for this, probably because the network card drivers were not installed yet.

After calling Microsoft and speaking to a computer that barely understands English, and then a human who barely understands English, my license was reactivated. After that it was just a matter of downloading all the drivers and rebooting a few times.

My copy of Windows 7 came from MSDNAA/ELMS. It probably would be different if I was using an OEM copy. From your post I'm guessing you are not using an OEM copy either.

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