In vista, network adapter, 6T04 has code 31. How to repair it.

http://answers.microsoft.com/en-us/windows/forum/windows_vista-windows_update/adaper-error-6t04-and-windows-update-error-code/09969726-6912-4b3e-9933-53308d45e901

Check this forum out, looks like that adapter is not needed http://www.vistax64.com/vista-networking-sharing/30771-microsoft-isatap-adapter.html

First remove the antivirus suites and firewalls. Open IE Go to Tools -> Internet Options -> Connections -> Lan Setup Check whether "USe proxy server..." check box is checked. If so untick it. Apply and Ok. Then check. If you are bot sure whether you have a proxy or not you can chose "Automatically detect settings". That will override manual configs how ever. Alternatively you can check Connection settings of Firefox since it is working.
Check the device manager for the adapter status. Right click on My computer and go to manage. If it has yellow exclamation marks or red X as you said that means a device failure or driver failure. If so you have to rollback the drivers and if it doesn't work uninstall and re install drivers. Use Add Remove programs if a software is there. If you use a software to configure / access the network appliance (if you have one like a wireless router) un install and re install it.
Check this thread as well.
This 6to4 adapter is a IPv6-to-IPv4 conversion layer. If you are not using IPv6 communications across IPv4 routers, you do not need 6to4 enabled. You can disable it. What is the IP address you are using? Is it ip v 4 or 6? Check using ipconfig using a command window (cmd.exe in run box and hit enter). Not necessary to use IPv6 (only if your college or etc etc use IPv6. Check this thread as well. isatap will not work on Vista but it doesn't do any harm though. :D
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To solve this problem with 6To4 adapter device with code 31, make sure you do the following:
1). Make sure you have all the updates installed for vista, such as, Important and Recommend updates.
2). [Right Click] my computer icon, and select (properties).
3). Select (Device Manager).
4). [Right Click] on the 6To4 icon, and select (Update Driver Software).
5). Click [Browse my computer for software drivers].
6). Click [Let me pick from a list of device drivers on my computer].
You should see the Microsoft 6To4 adapter listed?
If not you must uncheck the [] box show compatible hardware.
7). Then scroll down the list of Manufacture until you find (Microsoft), NOT Microsoft Corporation!
8). Click on (Microsoft) as the Manufacture and scroll down about two clicks, you should see 6To4 adapter.
9). [Left Click] on Microsoft 6To4 adapter and (Click Next), it should load the drivers as normally.

That 6to4 adapter has been a problem for as long as I have been aware of it but I only have that issue when I use my print server. I don't believe the 6to4 is your actual wireless. Are you using a wireless print server?

To resolve this concern, first thing to do is to uninstall the device from device manager and then after that restart the computer and run the setup cd that came with it to reinstall the software and the device back to your computer....

Check these things:

1. Is you Ethernet adapter Active
2. Is your Cable the correct one (NOT a cross over)
3. Refresh your IP Address for your Ethernet Card
4. Reboot your computer and power down your modem, then power the modem up AFTER your windows is logged on
5. Verify your modem "really" can connect, use another computer.
6. Verify the are no network issues with your ISP

check out the following link
http://www.errornerd.com/error.php?seed=Tunnel.sys&gclid=CKTH6oL245kCFQKaFQodonn0QQ
there are few steps need to perform to fix the problem.

Ok, first thing you need to do is, see if you network adapter is enabled ... You can do this in the Device manager. If there even is an adapter ... If there isn't download the drivers for your Ethernet card, put them on a mem stick and just install them on your Vista machine ...

http://forums.techguy.org/networking/592313-solved-6t04-adapter-fail.html