ipod touch/itunes is being retarded, please help!?

okay so me and my brother(hes 19) share the same pc computer and he has had his ipod for like 2/3 years and he got the ipodtouch right before me but he manajed to put all his music onto his ipod from his old itunes and thats the library that he uses for his itouch. well anyways, my mom's boyfriend ended up getting me an 8g ipod touch and my brother being so stupid went and plugged my ipod onto our computer and all his songs went onto my ipod and my cousin tryed to help me insstall my own version of itunes for the itouch so i could have my own account and when we went to install the program, it wasnt there and we already tried twice! im getting really fed up, whats the point of having an ipod if i cant evn have my own fucking music on it?! what do i do? should I have my brother burn all his songs onto discs and delete his itunes and then just sync his cd's back on and use limewire aa the same time try to install to windows of itunes or what?! help me if your a genius at itunes!