iTunes installation

When I install iTunes a window pops up and says that a script or something from windows installer package could not be run, then it starts rolling back action after that it keeps installing and installs "succesfully" but when I try to sync music into my iPod I get a window that says that the program or software that conects iTunes to iPod was not installed properly and it asks me to re-install iTunes, then everything starts again like a vicious circle. WHAT CAN I DO? my ipod is practically USELESS right now. Someone tell me please.