Dell vostro 1520 with built in wifi having issues connected please help

Hello! I have two issues with my windows vista dell vostro 1520 laptop. It has built in wifi but since I've gotten it I have never been able to access or see any connections when I try to connect t says there are none available althOugh my desktop and iPods connect fine and view them all. Is their a setting that wakes it up so it works? I have already switched the wifi switch back and forth and It doesn't change it's turned to on currently but little wifi symbol on keyboard does not light up.. Question 2: I have bought a USB d-link so I can connect to wifi box and I works at my house and hotels but will not connect to my moms house router box, it shows the networks available and will let me enter passcode to our router but once I press enter it shows me windows cannot connect and sends me to the connections page again... It's the right password has full bars of signal but will not connect!!! PRETTYPLEASE IF ANYONE CAN HELP SOLVE ONE OR BOTHOF MY ANSWERS I WOULD GREATLY APPRECIATE IT TY!