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<topic xml:lang="en-us" id="ts_win-guest-bluescreen">
  <title>Windows Fails After Changing VM Configuration</title>
  
  <body>
    <p>Changing certain virtual machine settings can cause Windows guests to fail during start up with a bluescreen. This may happen if you change VM settings after installing Windows, or if you copy a disk image with an already installed Windows to a newly created VM which has settings that differ from the original machine.</p>
    <p>This applies in particular to the following settings:</p>
    <ul>
      <li>
        <p>The ACPI and I/O APIC settings should never be changed after installing Windows. Depending on the presence of these hardware features, the Windows installation program chooses special kernel and device driver versions and will fail to startup should these hardware features be removed. Enabling them for a Windows VM which was installed without them does not cause any harm. However, Windows will not use these features in this case.</p>
      </li>
      <li>
        <p>Changing the storage controller hardware will cause bootup failures. This might also apply to you if you copy a disk image from an older version of <ph conkeyref="vbox-conkeyref-phrases/product-name"/> to a new virtual machine. The default subtype of IDE controller hardware used by <ph conkeyref="vbox-conkeyref-phrases/product-name"/> is PIIX4. Make sure that the storage controller settings are identical.</p>
      </li>
    </ul>
  </body>
  
</topic>
