Inspiron 1420 - Problem with accessing internet

My laptop is not able to access internet via both wired and wireless.  Connectivity is limited for both.

Network adapter was enabled.  Wireless switch was on.  Tried disabling McAfee firewall.  Able to identify and log in my security enabled network.  Followed manual to to disconnect modem cable & router & reconnect after 5mins.  Ran cmd, indicates IP routing & WINS proxy not enabled.  Plugged in USB adapter into laptop.  Signal strength remains strong through-out. 

My laptop is running on Windows Vista Home Premium.  A friend in the IT industry was unable to idenitify the problem.  He mentioned that something is blocking my laptop from receiving signals.  Appreciate any help on this as emails could not be sent to Dell as their email system is still unavailable till now & calling them proved to be futile as i do not have the express service code with me, just my service tag number.  Appreciate any help on this!