Is this a wired or wireless connection issue?
If it's a wireless issue, for now please remove the network encryption from the router, then see if you're able to connect. You also try a lower Security which is WEP.
If the above suggestion didn't work for you pls post an ipconfig /all:
Click on Start => in run or search box type cmd, enter. Open up a command prompt then Copy and Paste these ipconfig /all >c:\ipconfig.txt . Please attach the .txt file to be found in your Local Disk 'C' on your next post.
Please let us know.