on iTouch's the only music you can put it in, are the ones you buy from iTunes? Help!?

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Okay, so I'm planning to get an iTouch, and my brother has a ton of songs on his computer, but he didn't get them from iTunes, can I still put them in my iTouch? Also, can I just go to My Computer > Removable Disk (e): And just copy and paste the songs there? I'm new to this as you can tell lol.

Anyways, thanks.