You may see that error when you migrate virtual machine between two ESX servers with different hardware.
Please right click on VM and choose “Edit Options”, select “Options”, select “CPUID mask” and change it to “Hide the NX flag from quest”.
CPUID
It will give you more comparability between CPUs but will hurt performance.
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You can also just hide the offending register by using the advanced button. In this example, changing Level 0, ecx to HHHH HHHH HHH0 HHHH HHHH HHHH HHHH HHHH