I can't connect to my wireless network after I installed everything

Hello

I have a new XPS M1710 I want to connect to the internet and I wanted to have wireless network on where I can move free around the house with my computer

I have installed the software of the internet provider to configurate the moden and internet service, I have a Wireless-G Broadband Router attached to the the wireless moden router with the ethernet connected and also configured

My computer have a

Intel PRO/Wireless 3945 802.11a/g Mini Card (54Mbps) for XPS M1710

But still can't  be connected

What could be wrong?/

Thanks a lot for you help