Wut am i doin wrong

Hello,
i have a question for anyone with a answer deaing with the instalation of itunes. i bought my ipod offf of a friend w/ no instructions, everyone tells me that i have to down load itunes to instal media or music onto my device, and i was wondering if there was any other alternative to downloading things onto my ipod using like frostwire ofr any other website that wont give my computer a virus, hat i really wnt to do is install itunes, but everytime i clik download itunes 8.1 it downloads and then it ask me if i want to run(to instal the itunes 8.1) i click run and it just stop the screen that ask me if i wanna run it goes off and nothing happens. i even tried looking through my saved documents on my computer to see if it installd somewere on it, but i found nothin. can someone please help