My internet doesnt connect wirelessly! PLEASE HELP?

[bijx]

I am generally computer savvy and i know my way around a ton of problems, but one that has always caught me was the internet problems. i use an acer aspire running windows 7 and whenever i try connecting wirelessly to my internet, it gives me this image: http://i.imgur.com/EHxVqNm.png

I now have to connect with an ethernet cable and it is ok but i need the range and to be able to connect to a public network. There is also a light on my laptop that tells me if i have wireless turned on and it wont light up even though i turned it on.

My warranty has finished and i need help please! thank you