I would remove it it is not needed. Personally myself I do not think Microsoft should be allowed to download it on to your computer. Reformatted son in laws computer yesterday and when I started downloading windows Update I had to sign in after one lot of updates. And that was it ASP.NET had opened a new user account on the computer. Get rid or it will be wanting you to sign in every time you reboot the computer.
It usually opens the Welcome page with all user account Icons on it and you have to pick the one that you want it to open with. Thats how it works on XP. Like I said it is not needed so you have the option to remove or keep it.
[I'm having a similar problem as describe in your section regarding the asp.net account appearing in my "welcome" screen. My particular problem is that in the welcome screen, it request that I enter a password to access my own account. I have never set any password prior to this problem. Windows will not launch if I am not able to provide the right password. I have no idea what the password is. Please help. Thanks. ]
That was the one that that I got when it was first introduced. You had to sign in with a password and I could not remember ever putting a password on the computer. I was locked out of my computer for most of that day and more by luck than anything else I managed to bypass it in safe mode. If it is not doing you any harm leave it but some day it may want you to sign in with a password and if you don't know it you will be locked out of your computer.