To enable network DTC access and configure Windows Firewall on Windows Vista:

1. Click Start, click Run, type dcomcnfg and then click OK to open Component Services.
2. In the console tree, click to expand Component Services, click to expand Computers, click to expand My Computer, click to expand Distributed Transaction Coordinator and then click Local DTC.
3. Right click Local DTC and click Properties to display the Local DTC Properties dialog box.
4. Click the Security tab.

Set the following options on the Security tab of the Local DTC Properties dialog box and click OK.

1. Open the Control Panel, open Windows Firewall, and click Change settings to display Windows Firewall Settings.
2. Click the Exceptions tab.

Check the box for Distributed Transaction Coordinator and click OK.

Make sure you select Mutual Authentication on your Biztalk server DTC settings also.