Welcome to LQ!!
The questions you are asking are the type where you can ask 5 people and get 10 answers..
Dual-boot is useful if you need to use Windows a few times per week. If you need it a lot more often, you might want to look into a virtual machine setup. This lets you have Linux and Windows running at the same time.
For the standard MS SW, plus Photoshop and few other things, we have WINE or Crossover. This allows you to run these programs directly on Linux.
For i-tunes, I assume there are some native Linux solutions, but I have no direct knowledge. A search here or at Google will surely answer the question.