Ok I finally figured out the problem (sort of.) Although the Zonealarm firewall seemed to be configured correctly it was blocking internet access.  I uninstalled it, installed Comodo instead, and everything is working fine now.  Thanks for your suggestions.
I have 2 Dell computers in a home network.  In the past I was using both over a router in a wired LAN connected to a cable modem with no problems.  Then I noticed there was some unsecured wireless in my area so I shut off my cable and just used wireless for a while.  The wireless connection I was tapping into vanished so I just had the cable installed again, same provider, same setup. Now one computer (running Windows XP) connects fine while the other (XPS desktop running Windows 7) is not connecting to the internet.  The Network and Sharing Center shows internet access is active through the network, but I am not getting a connection on either IE or Firefox.  My firewall is allowing both of those programs to access the internet.  I heard there was a problem with McAfee but I'm using Avast antivirus. It shows no record of blocking a connection.  I've tried bypassing the router and going directly to the modem, booting in safe mode with networking, the flushdns method, uninstalling and reinstalling my Broadcam adapter etc, same result.  Since I'm no longer using wireless I disabled the wireless card.  Both IPv4 and IPv6 are set to obtain an IP and DNS address automatically.    I ran ipconfig /all and here are the results: Microsoft Windows [Version 6.1.7601]Copyright (c) 2009 Microsoft Corporation.  All rights reserved.C:\Windows\system32>ipconfig /allWindows IP Configuration   Host Name . . . . . . . . . . . . : LeftComputer   Primary Dns Suffix  . . . . . . . :   Node Type . . . . . . . . . . . . : Hybrid   IP Routing Enabled. . . . . . . . : No   WINS Proxy Enabled. . . . . . . . : No   DNS Suffix Search List. . . . . . : nyc.rr.comEthernet adapter Local Area Connection:   Connection-specific DNS Suffix  . : nyc.rr.com   Description . . . . . . . . . . . : Broadcom NetLink (TM) Gigabit Ethernet   Physical Address. . . . . . . . . : D4-BE-D9-9C-F4-7A   DHCP Enabled. . . . . . . . . . . : Yes   Autoconfiguration Enabled . . . . : Yes   Link-local IPv6 Address . . . . . : fe80::4590:b27c:a2a5:e24c%17(Preferred)   IPv4 Address. . . . . . . . . . . : 192.168.1.100(Preferred)   Subnet Mask . . . . . . . . . . . : 255.255.255.0   Lease Obtained. . . . . . . . . . : Sunday, November 04, 2012 4:51:43 PM   Lease Expires . . . . . . . . . . : Monday, November 05, 2012 4:51:43 PM   Default Gateway . . . . . . . . . : 192.168.1.1   DHCP Server . . . . . . . . . . . : 192.168.1.1   DHCPv6 IAID . . . . . . . . . . . : 399818457   DHCPv6 Client DUID. . . . . . . . : 00-01-00-01-16-E7-81-34-D4-BE-D9-9C-F4-7A   DNS Servers . . . . . . . . . . . : 209.18.47.61                                       209.18.47.62   NetBIOS over Tcpip. . . . . . . . : EnabledTunnel adapter isatap.nyc.rr.com:   Media State . . . . . . . . . . . : Media disconnected   Connection-specific DNS Suffix  . : nyc.rr.com   Description . . . . . . . . . . . : Microsoft ISATAP Adapter   Physical Address. . . . . . . . . : 00-00-00-00-00-00-00-E0   DHCP Enabled. . . . . . . . . . . : No   Autoconfiguration Enabled . . . . : YesTunnel adapter Local Area Connection* 9:   Media State . . . . . . . . . . . : Media disconnected   Connection-specific DNS Suffix  . :   Description . . . . . . . . . . . : Teredo Tunneling Pseudo-Interface   Physical Address. . . . . . . . . : 00-00-00-00-00-00-00-E0   DHCP Enabled. . . . . . . . . . . : No   Autoconfiguration Enabled . . . . : Yes Any thoughts on how to get me back up? Many thanks in advance.   
no internet over router on 1 pc, other pc does get internet