Internet help?

My laptop has trouble with the internet. When I first start the computer, the internet works great. I use internet explorer. I would like to use yahoo browser but somehow, I can’t download it. I have a CD but it’s corrupted. I tried downloading it from the Yahoo Software website, but it didn’t work. Anyways, if I hibernate my computer, and I use it again, the internet explorer won’t work.
It says:
The address is not valid. For every website, it says that. This problem occurs over and over. Please help me!!!
I tried to use the Windows connection diagnostic but it says
There might be a problem with one or more network adapters on this computer.
Then there’s three options:
briefly: turn on wireless capability – I use a DSL Modem – AT&T
automatically get new IP settings for the network adapter "Local Area Connection" – tried this numerous times doesn’t work
and: a problem with your network router or broadband modem might be preventing an internet connection
Please help!!!
My computer is 3 weeks old. How do I reinstall the adapters? I don’t even know what a network adapter is. Before I used to use the battery but now I charge it whenever I use it. One more thing, recently, like this week, I’m in the middle of browsing the internet, and it tells me my internet proxy server can’t be found or something similar. I’m so confused.

I did a clean install of Windows XP SP3 on my laptop and then when I went to my network connections my wireless is not showing up. I checked all the drives and they are fine and then network adaptor is fine but still not seeing my wireless tried to create a new wireless network and nothing still…I am not that computer savvy so just wanted to know if anyone knew what the problem could be?
It’s a gateway laptop MX6425– my router is a belkin…I’m on my desktop but have my laptop and there is no wireless connection showing only the Network Adapter Connection shows..I already did the whole Download the drives to flash drive then to laptop and still nothing. I looked in device manager and my network adapter is fine and disabled and enabled.
All the drives are installed and fine but still nothing, no wireless connection. I do appreciate the help guys!