Can't rename a file in Windows 7

When I try to delete a file in a folder which was created way before I had Windows 7 it says:

You need permission to perform this
action.

You require permission from the
computer's administrator to make
changes to this file.

But I AM the administrator. My account belongs to Administrators group. What the hell?

On a similar note, all the programs that don't have a GUI and are shell extensions can't create or modify files anywhere and Windows will never ask for my permission, so they basically won't work. How do I fix it?

The biggest question: why do I need to "run as administrator" when I am administrator already?

Answer

Have you tried to take ownership of the folders? Right-click > Properties > Security > Advanced > Owner and Take ownership as yourself (not administrator).