have you installed the .NET framework update from Windows Updates?
it's safe to delete this account in your user control panel if you want though before you do are you running xp home or profesional edition? i am informed that deleting it after installation on xp pro can cause a problem
remember that if you disable ityou cannot use the ASP.NET-capable server that makes use of Microsoft's .NET runtime (as opposed to its own runtime). .NET compiled applications should run fine.
have a look at the link below, that should explain more for you
define:ASP.NET - Google Search
hope that helps.
giles