Computer wont notice my iphone3g

Hello,
my iphone wont conect to my pc witch runs windows 7 and it should charge and ask me to import pics but it dont i downloaded itunes to put some shows that i got off the pirate bay and llime wire on it but when i plug my phone in nutting happens it seems like i netheer pluged my iphone in when i no i did what do i do i need help and i want to have more music on my iphone this is the first time i've ever conected my iphone to this computer and i have nether had itunes on any computer before so what do i do and the iphone works fine when i plug it on the wall and i have a iphone 3g so u no what kind i have