This applies to all versions of Windows 2003 and Windows 2008 and also to Vista and XP Professional. This problem normally occurs to our client with Dedicated Server hosting. So I thought I will create a check list to make their hosting service a bit easy.
Yes, you will need physical access to the machine to check this, it is obvious that you will not be able to check this problem unless you have remote access to the server. These steps can only be performed if you have physical access to the dedicated server or through a Keyboard-Video-Mouse [KVM]. So there we go:

* First thing that you need to check is whether the Remote Desktop Console [RDC] is enabled on your server.
Go to Desktop >> My Computer >> Properties >> Remote Tab
Check the box for “Enable Remote Desktop on this computer” and click OK.

* If the above option is enabled then make sure that the user which you are using to connect the server remotely is added in the “Remote Desktop users” group. Administrators are normally added in the group. This can be confirmed from with the steps below:
Go to Desktop >> My Computer >> Mange
Expand Local Users and Group >> Select Group.
Double click on “Remote Desktop Users” Group and make sure that the user is added in here.

* If both the above settings are correct then you need to make sure that TCP port 3389, which is the default port for RDC is enabled in the firewall of the machine that is used to RDP the server. Vise a verse make sure that the server firewall also has this port added in the exception. The best way to check this is:

First make sure that the server listens to telnet, try telnet of any other port which you are sure is working on the server like port 80 or 25. The command would be:

TELNET ip_address 25

If this works then try telnet on port 3389.

TELNET ip_address 3389

* If the telnet is not working then there are several possibilities, it can be the firewall on your machine or the firewall on the server tha is blocking the port. It can also be the case that Terminal Server Service did not start for some reasons. Or in a very rare situation it could be that the RDP port has been changed by some one. We will rectify all the possibilities one by one:

* Check the firewall on your machine or just shut the firewall down and then try the telnet again.

* If you have Windows Firewall then make sure that Remote Desktop is added in Exception.
Goto Start >> All Programs >> Control Panel >> Windows Firewall
If you have a third party firewall your dedicated server then just disable it and try the telnel option.

* If that is not the firewall issue make sure that Terminal Server Service is set to Automatic and is running. This server depends on Remote Procedure Call Service and you get errors while starting the server and you will need to trouble shoot the problem. If the server is terminating unexpectedly then make sure that the Hardware profile of the server is set to “Enable”:

* Sometimes client with Windows Dedicated Hosting package change the RDP port of their server and forget it, the steps below can be used for checking the RDP port as well as changing it as well, these steps will require to make changes in Registry hence it is recommended to backup the registry before following these steps:

Goto Start >> Run
Type: regedit to open the registry editor MMC
Expand to the Key:
[HKEY_LOCAL_MACHINESYSTEMCurrentControlSetControlTerminal ServerWinStationsRDP-Tcp]
Modify the value for Key “PortNumber”
Change Base to Decimal

Change Value data to the port your desire for your Dedicated Server
Click OK
Reboot the Machine.

Once the machine is online you will have to define your the port to connect your Dedicated Server remotrly
ip_address:port_number
10.10.10.52:3362

You must enable remote connections for each instance of SQL Server 2005 that you want to connect to from a remote computer. To do this, follow these steps:

1.    Click Start, point to Programs, point to Microsoft SQL Server 2005, point to Configuration Tools, and then click MS SQL Server Surface Area Configuration.
2.    On the MS SQL Server 2005 Surface Area Configuration page, click Surface Area Configuration for Services and Connections.
3.    On the Surface Area Configuration for Services and Connections page, expand Database Engine, click Remote Connections, click Local and remote connections, click the appropriate protocol to enable for your environment, and then click Apply.

Note Click OK when you receive the following message:
Changes to Connection Settings will not take effect until you restart the Database Engine service.
4.    On the Surface Area Configuration for Services and Connections page, expand Database Engine, click Service, click Stop, wait until the MSSQLSERVER service stops, and then click Start to restart the MSSQLSERVER service.

Enable the SQL Server Browser service

If you are running MS SQL Server 2005 by using an instance name and you are not using a specific TCP/IP port number in your connection string, you must enable the SQL Server Browser service to allow for remote connections. For example, MS SQL Server 2005 Express is installed with a default instance name of Computer Name\SQLEXPRESS. You are only required to enable the SQL Server Browser service one time, regardless of how many instances of SQL Server 2005 you are running. To enable the MS SQL Server Browser service, follow these steps.

Important These steps may increase your security risk. These steps may also make your computer or your network more vulnerable to attack by malicious users or by malicious software such as viruses. We recommend the process that this article describes to enable programs to operate as they are designed to, or to implement specific program capabilities. Before you make these changes, we recommend that you evaluate the risks that are associated with implementing this process in your particular environment. If you choose to implement this process, take any appropriate additional steps to help protect your system. We recommend that you use this process only if you really require this process.

1.    Click Start, point to Programs, point to Microsoft SQL Server 2005, point to Configuration Tools, and then click SQL Server Surface Area Configuration.
2.    On the MS SQL Server 2005 Surface Area Configuration page, click Surface Area Configuration for Services and Connections.
3.    On the Surface Area Configuration for Services and Connections page, click SQL Server Browser, click Automatic for Startup type, and then click Apply.

Note When you click the Automatic option, the SQL Server Browser service starts automatically every time that you start Microsoft Windows.
4.    Click Start, and then click OK.

Note When you run the MS SQL Server Browser service on a computer, the computer displays the instance names and the connection information for each instance of SQL Server that is running on the computer. This risk can be reduced by not enabling the SQL Server Browser service and by connecting to the instance of SQL Server directly through an assigned TCP port. Connecting directly to an instance of SQL Server through a TCP port is beyond the scope of this article. For more information about the SQL Server Browser server and connecting to an instance of SQL Server, see the following topics in SQL Server Books Online:

•    SQL Server Browser Service
•    Connecting to the SQL Server Database Engine
•    Client Network Configuration

Create exceptions in Windows Firewall

These steps apply to the version of Windows Firewall that is included in Windows XP Service Pack 2 (SP2) and in Windows Server 2003. If you are using a different firewall system, see your firewall documentation for more information.

If you are running a firewall on the computer that is running SQL Server 2005, external connections to SQL Server 2005 will be blocked unless SQL Server 2005 and the SQL Server Browser service can communicate through the firewall. You must create an exception for each instance of SQL Server 2005 that you want to accept remote connections and an exception for the SQL Server Browser service.

MS SQL Server 2005 uses an instance ID as part of the path when you install its program files. To create an exception for each instance of MS SQL Server, you must identify the correct instance ID. To obtain an instance ID, follow these steps:

1.    Click Start, point to Programs, point to Microsoft SQL Server 2005, point to Configuration Tools, and then click SQL Server Configuration Manager.
2.    In SQL Server Configuration Manager, click the SQL Server Browser service in the right pane, right-click the instance name in the main window, and then click Properties.
3.    On the SQL Server Browser Properties page, click the Advanced tab, locate the instance ID in the property list, and then click OK.

To open Windows Firewall, click Start, click Run, type firewall.cpl, and then click OK.

Create an exception for MS SQL Server 2005 in Windows Firewall

To create an exception for MS SQL Server 2005 in Windows Firewall, follow these steps:

1.    In Windows Firewall, click the Exceptions tab, and then click Add Program.
2.    In the Add a Program window, click Browse.
3.    Click the C:\Program Files\Microsoft SQL Server\MSSQL.1\MSSQL\Binn\sqlservr.exe executable program, click Open, and then click OK.

Note The path may be different depending on where SQL Server 2005 is installed. MSSQL.1 is a placeholder for the instance ID that you obtained in step 3 of the previous procedure.
4.    Repeat steps 1 through 3 for each instance of SQL Server 2005 that needs an exception.

Create an exception for the MS SQL Server Browser service in Windows Firewall

To create an exception for the SQL Server Browser service in Windows Firewall, follow these steps:

1.    In Windows Firewall, click the Exceptions tab, and then click Add Program.
2.    In the Add a Program window, click Browse.
3.    Click the C:\Program Files\Microsoft SQL Server\90\Shared\sqlbrowser.exe executable program, click Open, and then click OK.

Note The path may be different depending on where MS SQL Server 2005 is installed.