First, odds are you downloaded the .NET Framework, which adds the harmless account ASP.NET which causes this. You can delete the account if you wish, without any dire repercussions to your system.
Second, you can download TweakUI, or a dozen or so other programs that will set up an automatic login for you under XP. Add a password to your account just for the small bit of added security it provides, and then set up an automatic login.
I downloaded something from Microsoft, dont remember what, could have been the latest browser version, and when I did now I have to sign in my user account even tho I am the only person that uses this computer. I have XP Home and utilize Automatic Update function. I never use a password to sign on to my computer like some people do. I do not feel competent to go into the registery, so hope that will not be nessessary. JB