Try to just add the user to the group root with editing the /etc/passwd file with a text editor (of course as root). But I would not recommend making a normal user equivalent to root, because it makes your system more vurnerable to crackers etc. However, there might be other possible things to do here.
Code:
#su
#vim /etc/passwd
//change the line with
username:username ...
// or
username:users ...
// to
username:root
What distro are you using?
Permission in SuSe 9.2 Pro
