Why can't my laptop connect to the internet while connected to modem or wireless?

I have tried everything I could think of.. I've tried connecting straight to the modem, wireless router, going to work wireless router, going to wireless places.. and still no internet. It's not my modem because I can hook it up to my computer and it works fine. I have a Toshiba L305-S5903 laptop, windows vista. Can someone please help me???????