Hijacked Permissions

[rayben]

I am running Windows 7 ultimate on a Dell laptop computer. My permissions have been hijacked such that I can't access many of my folders and I can't update the permissions because "access is denied". Even my Recycle Bin has a lock symbol on it as do many of my file folders. I tried to load a program and got an error because the program couldn't write the necessary files in C:/Users directory. Does anyone know who/what has done this and how I can regain control of my own computer?
rayben