Had the same problem with one of the machines on a home network last week. The 'ASP.NET Machine A...' had sudenly appeared and insted of normal startup I had to log on. it also completely nadgered the network, PC would not talk unto PC. In the end had to uninstall the .NET thingy and remove the user. Now everything is OK again. It still begs the question, what the heck is it for and why did it suddenly install itself?