Changes that may help to increase the compatibility of Vista with older networking devices:
Disable the IP Helper service:
1. Go to Start and type in "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
1. Go to Start and type in "ncpa.cpl" (without the quotes) and press Enter
2. Right click on each network connection and select "Properties"
3. Remove the checkmark from the box next to "Internet Protocol Version 6 (TCP/IPv6)
4. Click OK to exit the dialog
NOTE: You should do this for each network connection.
Disable the DHCP Broadcast Flag:
1. Go to Start and type in "regedit" (without the quotes) and press Enter.
2. Locate and then click the following registry subkey:
In this registry path, click the (GUID) subkey that corresponds to the network adapter that is connected to the network.
3. On the Edit menu, point to New, and then click DWORD (32-bit) Value.
4. In the New Value #1 box, type DhcpConnDisableBcastFlagToggle, and then press ENTER.
5. Right-click DhcpConnDisableBcastFlagToggle, and then click Modify.
6. In the Value data box, type 1, and then click OK.
7. Close Registry Editor.
NOTE: You should do this for each and every GUID subkey.
The only program I'm aware of that currently relies on IPv6 is the new Windows Meeting Space. The first 2 changes will cause that program not to work - but will leave all of your normal (IPv4) connections unaffected. If it causes problems that you can't overcome, simply revert back to the original settings.