what is ip address is 0.0.0.0?

I work as an Technical Help desk agent and while Troubleshooting cases reg the connectivity of DSL people say they get the ip address 0.0.0.0 and so is the Subnetmask and Default gateway.Would that mean that the OS is looking at the dial adapter instead of the N/W adapter or the NIC is not functioning properly. would release and renew ip address work?
Some say ping 127.0.0.1 says nothing abt NIC. is it true?
does uninstall and reinstall TCP/IP work?

Nice Bunch of Question mate

Ok regrding the 0.0.0.0 ipaddress, whenever a client is set to obtain automatic ipaddress the 0.0.0.0 adress is show it is an unuseable invalid ip address at this point of time the client searches for dhcp (using bootp protocol i guess) when it finds the dhcp the dhcp offers an new ip address and the clients assings the ip address, otherwise after serveral retries if the client is not successfull in locating dhcp an APIPA(Automatic Private IP Addressing) is assigned as mentioned by sahir, or APIPA is assigned even when you are having 0.0.0.0 ip and clicked on repair of your adapters tcp/ip settings

ipconfig /release is used to unassign APIPA address
ipconfig /renew is used to get new ip address form isp dhcp server

127.0.0.1 is an reserved ip address used for diagnosis purpose it loopback and check whether TCP/IP protocol is installed correctly or not if no reply then you can reinstall TCP/IP protocol