The inability to run multiple concurrent websites from IIS under Windows XP is a pain. I need to run Server 2003 and IIS 6 to do that, and live with the resulting slowdown
There is a handy free utility, IISAdmin, which mitigates the worst aspect of the IIS 5 limitation: the need to reconfigure the Default Web Site each time I want to work with a different site. IISAdmin allows you to create new websites, each permanently pointing to a different set of files on disk. The limitation (probably in IIS 5 on XP) is that only a single site can be started at a time.