Windows Vista can't connect to internet...network adapter not working properly...can connect to internet in safe mode with networking...antivirus software disabled in normal mode

Hey,

Welcome to Microsoft Answers Forum!

I suggest you to follow the steps below in order to fix the issue you are experiencing:

Reset TCP\IP[ Transmission Control Protocol\Internet Protocol]:

To reset the TCP/IP stack go to this article and either click on "Fix it for me" or follow the instructions to fix it yourself:

http://support.microsoft.com/kb/299357

Disable the IP Helper service:

1. Hold the Windows key and type R, enter "services.msc" (without the quotes) and press Enter
2. Scroll down to the IP Helper service, right click on it and select Properties
3. In the dropdown box that says "Automatic" or "Manual", set it to Disabled and then click on "Apply"
4. Then click on "Stop" to stop the service from running in the current session
5. Click OK to exit the dialog

Disable IPv6:

Try uninstalling IPv6 on all interfaces, removing any IPv6 virtual adapters, and resetting the TCP/IP stack.  To remove IPv6, go into the properties for each network adapter and either uncheck the box next to the protocol "Internet Protocol version 6 (TCP/IPv6), that will disable it, or select it and click uninstall, which will remove it off the computer.  Then go into device manager and remove any 4to6 adapters, WUN miniport adapters, or tunnel adapters.

NOTE: You should do this for each network connection.

Disable the DHCP Broadcast Flag:

Link: http://support.microsoft.com/default.aspx/kb/928233

Important:  This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base:

322756 (http://support.microsoft.com/kb/322756/ ) How to back up and restore the registry in Windows

Windows Vista cannot obtain an IP address from certain routers or from certain non-Microsoft DHCP servers

To resolve this issue, disable the DHCP BROADCAST flag in Windows Vista. To do this, follow these steps:

1.       Click Start, type regedit in the Start Search box, and then click regedit in the Programs list.

2.       If you are prompted for an administrator password or for confirmation, type your password, or click Continue.

3.       Locate and then click the following registry subkey:

4.       HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\Interfaces{GUID}

5.       In this registry path, click the (GUID) subkey that corresponds to the network adapter that is connected to the network.

6.       On the Edit menu, point to New, and then click DWORD (32-bit) Value.

7.       In the New Value #1 box, type DhcpConnEnableBcastFlagToggle, and then press ENTER.

8.       Right-click DhcpConnEnableBcastFlagToggle, and then click Modify.

9.       In the Value data box, type 1, and then click OK.

10.   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.

To flush the DNS cache:

1.       Click Start, type cmd in the Start Search box, and then click cmd in the Programs list.

2.       If you are prompted for an Administrator Password or for confirmation, type your Password, or click Continue.

3.       Once at the Command Prompt, type ipconfig /flushdns

I hope the above information helps you.

Regards,

Manasa P- Microsoft Support.