I have win xp home and have just been looking at my user accounts and I have an account called asp.net machine a... I have not created this account and it does not appear on the welcome screen when the computer stats up. Should I delete this account or is it there for some special reason?
The aspnet_wp or ASP.NET Machine Account is created when the Microsoft .Net Framework 1.1 is installed onto a Windows XP computer. The user is created for the asp.net worker process used in Microsoft's Internet Information Services to fully support ASP.net on your web server. There is not a need to worry about this users presence, it was not created in malicious way.
ASP.net is a programming framework built on the common language runtime (Microsoft .net framework) that can be used on a server to build powerful Web applications. For more information on ASP.net see here
Why does it need another User Account?
Another user account is created for the ASP. Net Worker Process (Aspnet_wp.exe) so that it is not running with administrator privileges. This helps to increase security because if there was a breach the worker process is running as a lowly restricted user rather than having administrator privileges on the local machine.