Why did the developers set this to default true and not allow the user to change it?

Here’s the fix via the VirtualBox Forums from user ykee

Modify the machines’s xml file

Change

<HardwareVirtEx enabled=”true”/>

TO

<HardwareVirtEx />

“the source code says that the default value is “false”, and this is how you force the program to use the default value.”

VirtualBox 2.2.2 VT-X True but Greyed Out Fix originally appeared on Shai Perednik.com on May 15, 2009.