You can use same settings as IIS 6 to configure IIS 5.1, map .* to aspnet_isapi.dll, like any other ASP.NET handler.
1. Open IIS Manager. Make sure it’s the OLD IIS manager that comes with XP. If you go to Help -> About Internet Information Services it should show version 5.1, not 6.0.
2. Right-click your virtual directory application and hit PropertiesIf it isn’t already, make sure the virtual directory is an Application
3. Click Configuration.Find out what the DLL path for .aspx is by selecting it from the list and click edit.
4. Add a new extension, putting the path from the .aspx extension in the Executable field.
5. In the extension field, put “.*” (without quotes). uncheck “Check that file exists.” click OK.
6. Save your settings and it should work!