PLEASE HELP ME FIGURE OUT ITUNES.?

okay im having a lott of trouble . i really dont know why its doing it . its bothering the heck outta me . so this iswhat is happpending . hwhen i plug my ipod touch into my computer. it doesnt have like my ipod touch showing up it just said what i lke purshaced , & i cant likemake it downlde the 3.0 or 4.0 generationg pleasr plase helppp me