A short Linux/Ubuntu tip:
If you want to control what services (daemons in Linux speak) run when you start your computer, use sudo sysv-rc-conf from the command line. If you don’t have it installed, do a quick sudo apt-get install sysv-rc-conf. It’s a very small download (around 25 Kb) and it’s much more convenient than fiddling with the init scripts. A word of warning though: if you don’t know what you are doing, be very, very careful, since you can make your computer unusable very fast. Below are two tutorials about the Linux boot process which should help you understand what you’re tinkering with: