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IP changes to a static IP, a static IP and an alternate IP remain on the Network Interface
http://www.vistaarticles.com/articles/261/1/IP-changes-to-a-static-IP%2C-a-static-IP-and-an-alternate-IP-remain-on-the-Network-Interface
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Published on 12/10/2006
 
When the IP address configuration changes from an alternate IP address to a static IP address in Windows Vista, both the alternate IP address and the static IP address remain on the network interface.

IP changes to a static IP, a static IP and an alternate IP remain on the Network Interface

To resolve this problem, follow these steps:1. Log on to the Windows Vista client computer as a user who is a member of the Administrators group. 
2. Open the Network Connections folder. To do this, click Start, type ncpa.cpl in the Start Search box, and then press ENTER.

If the User Account Control dialog box prompts you to elevate your administrator token, click Continue. 
3. Right-click the network interface, and then click Properties.
4. Click Internet Protocol Version 4 (TCP/IPv4), and then click Properties.
5. Click the Alternate Configuration tab, and then click Automatic private IP address.
6. Click the General tab, click Obtain an IP address automatically, and then click OK two times.
7. Open the Network Connections folder again.
8. Right-click the network interface, and then click Properties.
9. Click Internet Protocol Version 4 (TCP/IPv4), and then click Properties.
10. Configure a static IP address, and then click OK two times.