I have sa account and I tried to enable it but same problem not allowing to do any action error stating either sa account does not exists or user(machinename/administrator) do not have permission.

I tried to repair sql by going to control panel-from addremove progrmes-but then it is asking for valid path of installation media which I could not find.

So is their any other way to resolve this issue?

I remember I had unchecked sysadmin checkbox in server roles for the default administrator account is that giving problem for not allowing any action?