Dear Jothi,

Hope you are doing well.

Please go through the steps given below
Method 1 :

1)Select the Virtual device and choose Settings
2)Navigate to System and click the Processor tab
3)Tick the check-box, Enable PAE/NX
4)Click OK and you are done

If the Method 1 not working for you then try the Method 2 :

Before the PC opens --> Press F2 to open boot menu--> Settings --> Configuration --> Intel Virtual Technology: [ENABLED]

Please let me know if the issue still persists.

Feel free to contact us in case you have any query. 
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