I can't install some prgorams after fixing my MacBook?

My MacBook broke so i sent it compume (dealer) and finally fixed it.

However the user name and password were changed, they simply removed the entire hard disk and installed another one with another name. needless to say, that pissed me off.

after reinstalling OSX I changed my user name and password (and yet the bluetooth devices list shows "macbook's computer" instead of "evanescfan's computer" nevermind)

thing is, i created a new account before reinstalling, and couldn't delete either the old account or this account, so i reinstalled the OSX then. now i have only one admin account; evanescfan. but every time i try to install flash player it sez "u don't have enough access privilege to do this installation" or something. same thing happened with firefox3 when i tried to get it from download.com.

another thing; i think i can't update any of my personal programs, not the Apple ones. the update option is disabled in most of the programs if not all.

one more thing: I AM the only user.