Did you install the network driver for your wireless or ethernet device from the HP downloads for your model, or was it provided already by the installer?
Did the network then show up in the bottom-right System tray? What happened if you tried to connect?
Next rightclick on the network connection icon in System tray to Troubleshoot. Report back results.
Have you installed all Important and Optional Windows Updates and completed the other Best Practices for Clean Reinstall - Factory OEM Windows 7