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 Vistca, 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
type regedit in the Start Search box, and then click regedit in the Programs list.
If you are prompted for an administrator password or for confirmation, type your password, or click Continue.
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Locate and then click the following registry subkey:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\Interfaces\{GUID}
In this registry path, click the (GUID) subkey that corresponds to the network adapter that is connected to the network.
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On the Edit menu, point to New, and then click DWORD (32-bit) Value.
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In the New Value #1 box, type DhcpConnEnableBcastFlagToggle, and then press ENTER.
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Right-click DhcpConnEnableBcastFlagToggle, and then click Modify.
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In the Value data box, type 1, and then click OK.
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Close Registry Editor.
By setting this registry key to 1, Windows Vista will first try to obtain an IP address by using the BROADCAST flag in DHCP Discover packets. If that fails, it will try to obtain an IP address without using the BROADCAST flag in DHCP Discover packets.