Windows cannot be installed on VirtualBox, CompareExchange128 Processor Incompatibility

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A few days ago, we reported a bug we just had when installing Windows 8.1 Preview on VirtualBox. As we all know, VirtualBox is the safest way to try preview versions, as it provides all the necessary requirements for the Windows edition to be tested. Today we had another problem with the installation of Windows 8.1 on VirtualBox. This time we have an error window: Your PC does not support CompareExchange128. Here is the screenshot:

This seems to be a compatibility issue closely related to virtualization, since Windows 8 runs on the same PC. However, VirtualBox settings must be respected if you decide to install an operating system, in addition to the normal requirements specified for this. VirtualBox has a solution for that.

The patch is mentioned below, but make sure you run it if VirtualBox doesn’t work on your system.

Windows cannot be installed because the processor does not support CompareExchange128

January 2021 Update:

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  • Step 1 : Download PC Repair & Optimizer Tool (Windows 10, 8, 7, XP, Vista – Microsoft Gold Certified).
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1 Open Prompt Command with administrative rights.

2 Enter these commands one by one, then Enter key :

cd'C:Program FilesOracleVirtualBox'. ] VBoxIntern/CPUM/CMPXCHG16B 1

User (not administrative Command prompt). Restart and try installing Windows 8.1 using virtualization, and this time you will not get the error.

This article refers to 32-bit preview of Windows 8.1, if you want to install 64-bit version Windows 8.1, then your processor must support CMPXCHG16b, PrefetchW and LAHF/SAHF.

I hope you find the solution useful!

If you receive the error message’Your Windows installation could not complete’, check this message.

RECOMMENDED: Click here to troubleshoot Windows errors and optimize system performance

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