HELP! home wireless not found, others are!!

ok so my little sister just got a used hp compaq nx5000 from my aunt and uncle it ran fine on their home network but they put windows 7 on it for my little sister and now it will not connect at all wirlessly. i dont a clean install of windows xp because i thought that may be the problem but that didn’t work, i have whent through all the internet connections and setups and repair, troubleshoot, changed my security settings, and everything i cant think of i also reset my router and modem, i know a little about computer”not a whole lot” and i cannot fiqure this out can anyone PLEASE help!