Source: http://technet.microsoft.com/en-us/library/cc754203%28v=ws.10%29.aspx

Windows Server 2008

Membership in Administrators, or equivalent, is the minimum required to perform these procedures.
To configure a static IP address on a computer running Windows Server 2008

1. Click Start, and then click Control Panel.
2. In Control Panel, verify that Classic View is selected, and then double-click Network and Sharing Center.
3. In Network and Sharing Center, in Tasks, click Manage Network Connections.
4. In Network Connections, right-click the network connection that you want to configure, and then click Properties.
5. In Local Area Connection Properties, in This connection uses the following items, select Internet Protocol Version 4 (TCP/IPv4), and then click Properties. The Internet Protocol Version 4 (TCP/IPv4) Properties dialog box opens.
6. In Internet Protocol Version 4 (TCP/IPv4) Properties, on the General tab, click Use the following IP address. In IP address, type the IP address that you want to use.
7. Press tab to place the cursor in Subnet mask. A default value for subnet mask is entered automatically. Either accept the default subnet mask, or type the subnet mask that you want to use.
8. In Default gateway, type the IP address of your default gateway.
9. In Preferred DNS server, type the IP address of your DNS server. If you plan to use the local computer as the preferred DNS server, type the IP address of the local computer.
10. In Alternate DNS Server, type the IP address of your alternate DNS server, if any. If you plan to use the local computer as an alternate DNS server, type the IP address of the local computer.

Click OK, and then click Close.

Windows Server 2003

Membership in Administrators, or equivalent, is the minimum required to perform these procedures.
To configure a static IP address on a computer running Windows Server 2003

1. Click Start, click Control Panel, right-click Network Connections, and then click Open.
2. In Network Connections, right-click the network connection that you want to configure, and then click Properties.
3. In Local Area Connection Properties, in This Connection uses the following Items, select Internet Protocol (TCP/IP), and then click Properties. The Internet Protocol (TCP) Properties dialog box opens.
4. In Internet Protocol Version 4 (TCP/IPv4) Properties, on the General tab, click Use the following IP address. In IP address, type the IP address that you want to use.
5. In Subnet mask, either accept the default subnet mask, or type the subnet mask that you want to use.
6. In Default gateway, type the IP address of your default gateway.
7. In Preferred DNS server, type the IP address of your DNS server.
8. In Alternate DNS Server, type the IP address of your alternate DNS server, if any.

Click OK, and then click Close.