new hero user.... quick question

[setix]

I just got my Hero for christmas, and Im loving it so far. I have a question about apps running in the back ground.

Ive rooted my phone and am still running the stock firmware, and I have Advanced Task Killer installed to kill back ground apps. Sometimes when i open it to kill programs, there are programs that I havent opened that are running, such as sprint nav and voice dialer.

is this normal for apps to open, or do they open because other apps need to run those programs in order to function (ie- layars, bonsai blast, es file explorer)?

thanks