Hello Adewale,
Thank you for visiting Microsoft Community Forum.
As per the description, I understand that turning on Hyper-V disables nVidia GPU on your Windows 8.1 computer, you need to have both of them running.
The question that you asked is more suited to Microsoft TechNet forum. We have a dedicated forum support for Hyper-v and related issues, I would suggest you to post your query on Microsoft TechNet forum for this issue. There you can get more effective and appropriate suggestions by experts familiar with this topic. Your understanding is appreciated.
Here is the link for Microsoft TechNet forum:
http://social.technet.microsoft.com/Forums/windows/en-US/home?category=w8itpro
Hope this information is helpful. Please write back to us if you have any other query or for any further assistance, we’ll be glad to assist you.