I miss the straightforward diagnostics of Windows XP, but Windows 7 does have some network diagnostics you can try (depending on whether you have Category or Icon view):

Control Panel > Network and Internet > "View network status and tasks"
Control Panel > Network and Sharing Center

If you click an active connection link, a dialog should open with a Diagnose button toward the bottom.

You might need to enable the DHCP server in the router, if it has one. I had to set that up for my computer. Getting access to the router settings might be tricky. Try shutting off the router and the PC, then start them both up and see if you can get into the router settings with the browser.

See also:

• http://technet.microsoft.com/en-us/library/bb490939.aspx
• http://technet.microsoft.com/en-us/library/bb490947.aspx