Try these simple tests.
Hold the Windows key and press R, then type CMD (COMMAND for W98/WME) to open a command prompt:
In the command prompt window that opens, type type the following commands one at a time, followed by the Enter key:
NOTE: For the items below in red surrounded with < >, see comments below for the actual information content, they are value substitutions from the previous IPCONFIG command output! Do NOT type <computer_IP_address> into the command, that won't work. Also, the < and > in the text is to identify the parameters, they are also NOT used in the actual commands.
Do NOT include the <> either, they're just to identify the values for substitution.
Right click in the command window and choose Select All, then hit Enter to copy the contents to the clipboard.
Paste the results in a message here.
<computer_IP_address> - The IP Address of your computer, obtained from the IPCONFIG command above. (For Vista/Win7, the IPv4 Address)
<default_gateway_address> - The IP address of the Default Gateway, obtained from the IPCONFIG command above.
<dns_servers> - The IP address of the first (or only) address for DNS Servers, obtained from the IPCONFIG command above.
If you are on a machine with no network connection, use a floppy, USB disk, or a CD-RW disk to transfer a text file with the information to allow pasting it here.