Error "Network not found" while joining a domain

Cant Join a Domain?

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The primary cause (99.99% of the time) a Client cannot connect to a domain its DNS related.

To Troubleshoot you need to know the IP address of your DNS server, In many cases its on the first domain controller but that's not always the case so find out (go to a WORKING client or Server) and do the following.
Start > run > cmd {enter}
ipconfig /all {enter}

Now take note of the following entries

DNS Servers . . . . . . . . . . . : <ip address of your DNS server>

Go back to the FAULTY client and ensure that this IP has been set on its TCP/IP Properties

Win XP: Start > Control Panel > Network Connections > right click > Properties > scroll down to TCP/IP > Properties

You will notice there are two settings, 1. Automatically detect DNS server (only use if your network uses DHCP and has been configured to Lease out DNS details) 2. "Use the following DNS server addresses" Here you need to type in the IP address(s) of your DNS server(s) you can also enter the IP address of your domain controller NB if you need to add more than two addresses, then click Advanced > DNS, and enter as many as you like.
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OK Now we have ascertained the client has the correct DNS settings you need to make sure the client can actually "See" the DNS server.

1. Test physical connection to the server
Start > Run > CMD {enter}
ping <insert_ip_address_of_DNS_server>
If you get 4x replies then we are cooking on gas (go to Number 3)
2. If your here then number one was unsuccessful download and run this from my website http://www.petenetlive.com/Downloads/software/WinsockFix.exe and go back to number 1 (if it continually fails you have a problem with the cabling, or your NIC card)
3. Test DNS is working
Start > Run > CMD {enter}
ping <name_of_DNS_server>
or
ping www.cisco.com {enter}  <--- note only works if you have internet access
If either of these was successful then go to number 5
4. DNS is not resolving
Start > Run > CMD {enter}
nslookup <name of your domain controller> {enter}
or
nslookup www.google.com {enter}
The above should return the IP address if it doesnt check the DNS server is up, and the DNS service is running (net start command on the server will tell you)
5. If your here then DNS is running fine.
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If you got this far then the next most likely candidate is the computer name already exists in the domain you are trying to join. On the CLIENT find out its computer name.
Start > Run > CMD {enter}
echo %computername%
Write this down. Go to the domain controller and do the following
Start > Run > dsa.msc {enter}
When the Active Directory Users and Computers console opens expand the "Computers" OU and locate the entry that is the same as the name of the client > highlight it and press the delete key.
Now Go back to the client and try to join the domain.
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Cannot Join Domain Because of SMB Signing
http://support.microsoft.com/kb/q199714/

Error Message: System Cannot Log You on Because Domain <Computername> Is Not Available
http://support.microsoft.com/kb/q244671/