Microsoft Knowledge Base Article 887489 contains the following intoduction:
This article describes some of the connectivity and authentication issues that you may experience when you install Microsoft Virtual Server 2005 on a Microsoft Windows XP-based computer that has been upgraded to Windows XP Service Pack 2 (SP2).
Microsoft does provide support for running Virtual Server on a Windows XP-based computer in a non-production, development or test environment. The information in this article may provide assistance when evaluating Virtual Server on a Windows XP Professional SP2-based computer in one of these development or test environments.
Important When you open ports in your firewall, you increase the chance that other programs may gain access to your computer through those ports. Because of this, we recommend that you carefully consider your network security requirements before you open ports in your firewall. You may want to only open the port when you are using the program and close the port when you are not using the program.