while manipulating with properties of c drive,i accidentally denied all permissions of authenicated users,now i couldn't able to access c drive and its files,and i couldn't able to change those permissions also.please help me resolve this...

Hi,

So are we still using the administrator account?

We might take use of the built-in administrator to recheck the drive permissions:

Run the bellow command from command line using admin rights:

Net user administrator /active:yes

Then login and check the permissions with the Administrator account.

Best regards

I appreciate the help but unfortunately I have the same issue.  When I tried the following command this shows up after pressing enter

System error 5 has occurred

Access is denied

If I try to run cmd as Admin my computer denies access to that as well. Please reply I can't Install windows 10 because of this Issue. I have tried to regain ownership but changing the owner also has access denied as well. Any program associated with admin rights is denied.