You'll need to provide administrator permission to copy this file

While I was saving a files downloaded from internet, I got this error message "You'll need to provide administrator permission to copy this file" in Windows 7. When I was copying some files from my external HD, "you'll need to provide administrator permission to move to this folder" appeared. And I deleted an AVI file created with CamStudio, computer says "You'll need to provide administrator permission to delete this file" with the choices "Continue", "Skip", and "Cancel". After I choose "Continue", the Windows 7 system OS gives me others following message :

"File Access Denied"
"You need permission to perform this action"
"You require permission from the computer's administrator to make changes to this file"

Can anyone help me to solve these?

Try it:

Right click on the folder you want to delete or copy to ( or the drive in "my computer")--> Under the security tab choose "edit" --> Go to the "Users (***/users) where the * are the name of your login --> Tick the box which says "full control".