hello...
this is going to drive you crazy unless you take some time to understand permissions and where different levels of users are allowed to interact with the system...
unfortunately, it's _way_ beyond the scope of a remote forum to explain how this works - basically, different users have different rights and each file and directory on the system is owned by somebody - after that, permissions are set for group access and all others...
i would start here and read up on how all this works:
http://www.osxfaq.com/Tutorials/LearningCenter/UnixTutorials/ManagingPermis...
as an admin, you had much more freedom on the box - as a plain user, you have much less...
the reason i can't really get into helping you on your specific case is that i have no idea who owns what where on your box - and posting back and forth here won't clear that up... :-/
sitruc