After connecting your vista machine to your router it may not get the ip address from your DHCP server in this case this tutorial will help you to fix this issue.
Consider the following scenario
• You connect a Windows Vista-based computer to a network.
• A router or other device that is configured as a Dynamic Host Configuration Protocol (DHCP) server is configured on the network.
• The router or the other device does not support the DHCP BROADCAST flag.
In this scenario, Windows Vista cannot obtain an IP address.
Cause for the above problem
This issue occurs because of a difference in design between Windows Vista and Microsoft Windows XP Service Pack 2 (SP2). Specifically, in Windows XP SP2, the BROADCAST flag in DHCP discovery packets is set to 0 (disabled). In Windows Vista, the BROADCAST flag in DHCP discovery packets is not disabled. Therefore, some routers and some non-Microsoft DHCP servers cannot process the DHCP discovery packets.
To resolve this issue, disable the DHCP BROADCAST flag in Windows Vista. To do this, follow these steps
Click Start–>Run type regedit click ok
If you are prompted for an administrator password or for confirmation, type your password, or click Continue.
Locate and then click the following registry subkey from left pane
In this registry path, click the (GUID) subkey that corresponds to the network adapter that is connected to the network.
On the Edit menu, point to New, and then click DWORD (32-bit) Value.
In the New Value #1 box, type DhcpConnEnableBcastFlagToggle, and then press ENTER.
Right-click DhcpConnEnableBcastFlagToggle, and then click Modify.
In the Value data box, type 1, and then click OK.
Close Registry Editor.