Problem with the administrative priviledges even though the admin

I am using windows 7 starter. i am the administrator of my PC. I am the only user on my PC. but i do not have the administrative priviledges. i cant even copy anything to C and D drives because i do not have the write privileges.Please help me...... when i right click on computer, and say manage, a message such as "Windows cannot find "". Make sure that you have typed the name correctly and try again" is displayed. i do not have even the right to install anything.

I am having a similar issue when I try to make changes through the command prompt. It says that I need to run as an administrator. I have gone through the steps of making myself the administrator, which I already was, but it is still insisting that I am not. How to I fix this?

I had downloaded NPAV antivirus from its official website and right clicked on it and said "Run as administrator". After the installation, the system was restarted and now i do not have any of the administrative priviledges. i cant even copy to C and D drives...

how to find who is the administrator of our PC? In user accounts it is shown that i am the administrator. But after installing downloaded npav i cant even copy to my c and d drives and even cant install any programs....