Change the HAL from multiprocessor to uniprocessor on a Windows 2003 Virtual Machine.

When performing a P2V or a V2V migration process, it’s a good opportunity to reduce the number of processors that the virtual machine will use. When you are migrating a multiprocessor server to a uniprocessor virtual machine, keep in mind that the HAL of the virtual machine needs to be changed from multi to uniprocessor. So, when the migration process is finished and the virtual machine is running, follow these steps to change the HAL from multiprocessor to uniprocessor.

  1. Login to the VM with the Administrator account.
  2. Open the device manager (devmgmt.msc).
  3. Select the processor and right-click to update the driver.
  4. In the Hardware Update Wizard, choose “No, not this time” and click Next.
  5. In the next window choose “Install from a list or specific location” and click Next.
  6. Select “Don’t search. I will choose the driver to install” ratio button and click Next.
  7. In the list with compatible hardware, select the Uniprocessor PC and click Next.
  8. When the wizard completes, click Finish to end the Hardware Update Wizard and restart your VM.
  9. Done.


– Marek.Z


    • Hi Daniel,

      Thanks for pointing that out but in this case the processor type was ACPI and it is possible to change it from multi- to uni-processor (according to the options described in the KB309283). I agree with you that is not supported though. However, it’s commonly accepted in the visualization community.

      In case of W2k8, the HAL changes automatically after you P2V a machine so there is no need to change it manually.


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