If I am running MS Windows 7 in a VM, what changes or upgrades might cause the Windows license to be invalidated? The full retail version of Windows 7 is no longer available, so I have to use the OEM version. The host OS will be CentOS 6. What I don't know is what characteristics of the underlying hardware and host OS are visible to the guest and would void that OEM restricted license should they change.

• Hopefully, a point release upgrade of the host OS would not be a problem, but what about going from CentOS 6 to CentOS 7?
• How much of the bare iron is visible to the guest? Would a motherboard upgrade (same CPU type) be seen? (That invalidates an OEM install.)
• Right now I'm mainly looking at KVM. Would VirtualBox or VMware be any different in that respect?

This is not something I can experiment with without wasting costly Windows validation codes, so I'm looking for advice here.

Upgrading the host os should not pose a problem to a Windows 7 guest OS's license mechanism.

OEM license is invalid on a virtual machine, period.

(edit)

It appears I am incorrect according to: http://www.microsoft.com/oem/en/Page...id=tANZJoRL_hh

Apologies for the bad advice!

As stated already by Habitual, the host OS can not be seen at all by the guest OS, so upgrades are irrelevant.
The CPU is the only thing that is visible. Also, keep in mind that OEM does not by definition mean that the OS is tied to the hardware. While there are such versions, many are not, especially if you got that machine from one of the smaller OEMs.
Yes. KVM/Qemu currently has no working 3D acceleration, while Virtualbox and VMware products have. According to some benchmarks, you will get better performance in general with KVM and VMware products, compared to Virtualbox, but if you need 3D for your workflow KVM is a no-go (for now, there is work getting that done).

Thanks. I'll be installing a newly purchased copy of Windows 7 OEM. The machine I'm using is one I assembled myself a couple of years ago.

Here's the situation. I've got an old, relatively weak machine that I've been keeping around solely for its Windows XP license and use only for things like TurboTax that absolutely require MS Windows. I want to get rid of that machine and use a VM running Windows 7 for those tasks. The new(er) machine has had a partition set aside for Windows ever since I built it, but no version of Windows has ever been installed.

I appreciate your assessment of relative graphics performance. The target machine is already pretty weak in that department (embedded ATI Radeon HD 3300 graphics on the MB), so that is a concern. At least I can experiment with the various VM options before registering the installation with MS.

Most true OEM copies are not real copies from MS. They are bought in mass and have phoney numbers that the company that sold it to you has. It authenticates to some set of hardware on the computer.

Now you may have a builders or other dvd but I'd doubt you could take a dvd from Dell and get it to run.

Mine were bought from a reputable supplier that has always stood behind the thousands of dollars worth of equipment I have purchased from them in the past. It's not some eBay store or 3rd party Amazon seller.

In that case you will most likely have a version without hardware ties. You can install that on any machine/VM. Changing components may require to re-activate the installation, but that poses no problem. I use such versions myself and never had a problem.

That is the problem with this OEM designation. Microsoft may sell a dvd to end users and label it OEM. They require sellers to make you buy some hardware usually with the purchase. Most people would consider OEM as meaning a disc that came a computer from a company such as Dell or HP.

If you've used these disc's then you would have had to authenticate it. I've run builders windows copies in VM's just fine.

FWIW, I installed one of the copies on my Lenovo laptop (on the hardware -- no VM), and the product key was accepted no problemo. That's unlike what happened when I tried to reinstall Windows XP on that laptop using the key from the sticker on the bottom. It's one of those "XP downgrade from Vista" machines. I suppose I'd have to install Vista and then downgrade to make that work.

The only problem I did have was that the install + 106 security updates beat on the disk so hard that it overheated and logged a SMART "end-to-end error". The "1" in that counter will forever cause smartctl to report that the drive is "FAILING NOW" thanks to Seagate setting the failure threshold so tight. Oh well, "Live and yearn," as the saying should go.

At one time there was some discussion about loading Windows 7 to a vm. Think MS reversed their complaint about it.

Updating the host OS isn't the problem, however updating the VM software, which happens sometimes with the OS update, can be a problem, or so have anecdotal reports stated. The guest sees the emulated hardware. Consider KVM: you can run the standard 440bx chipset or the new q35 chipset option. Windows will see a whole new motherboard. I've seen a similar problem with VMWare, which typically has to be recompiled for each new kernel of the host OS, so that you can't be conservative and keep your emulator the same. Therefore, I'd recommend qemu with KVM or Xen.

BTW: They both allow emulated graphics cards or passed through real graphics cards.

Those are the issues that worry me. You recommend KVM, but that is built into the kernel, so might I not find that a kernel update includes some change to the hypervisor visible to the guest and invalidates my Windows license? I certainly don't want to find myself locked out from doing an important kernel update.

Well that's just the thing: if you use KVM or Xen, you can change the kernel as often as you want and not change qemu, hence the Windows guest won't see any difference. If you use VBox or VMware, you'll have to update them/recompile their module every time there's a kernel change, assuming there is a patch (which for VMWare is a big IF). If you use the Guest Additions, which of course you'll want, the new drivers will be recognized by Windows as new hardware and you'll be up the creek, perhaps. If you use qemu under KVM or Xen, it'll only be if you change qemu that you might have problems, and you will not have to change qemu when you change kernels.

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That certainly sounds like KVM or Xen would be the safest bet from a license standpoint. Hopefully the emulated graphics performance will be "good enough." I'll be wanting to run the VM in a window most of the time, so passing through the real graphics card isn't an option.

I haven't really looked at Xen. Hasn't it been pretty much superseded by KVM?