Windows 7 has the concept of an "Alternate Configuration" in the network card's IP configuration. From the Windows Help page for "IPv4 Alternate Configuration Tab":
User configured specifies that IPv4 will use a manually specified
configuration if a DHCP server is not found. This alternate
configuration is useful when the computer is used on more than one
network, at least one of the networks does not have a DHCP server, and
an APIPA configuration is not wanted. A good example is a portable
computer that is used at the office and at home. At the office, the
laptop uses a DHCP-allocated TCP/IP configuration. At home, where
there is no DHCP server present, the portable computer automatically
uses the alternate configuration, allowing easy access to home network
devices and the Internet. This enables the portable computer to
operate seamlessly on both networks without manual IP reconfiguration.
Set this up by going to Control Panel -> Network status and tasks (or "Network and Sharing Centre" if you're not using the category view).
Click the connection name that you're interested in (probably "Local Area Connection" or "Wireless Network Connection (network name)").
This should pop up the Connection Status window, click the Properties button.
In the Connection Properties window, look for the "Internet Protocol Version 4 (TCP/IPv4)" line, click that and click Properties.
You should now have a window with two tabs, one of which is "General", the other is "Alternate Configuration".
You can now set the first tab to use DHCP (select "Obtain an IP address automatically" and "Obtain DNS server address automatically") and put your static IP details into the second "Alternate Configuration" tab.
More from Technet IPv4 Alternate Configuration Tab and elsewhere on SuperUser What is the "Alternate Configuration" tab in TCP/IP settings