That depends... Is it another person or something like ASP.Net?
If it is another person, just delete their account or change their password and never tell them what it is.
If it is a System account, best leave it alone. Things like Framework may establish an internal admin account to make what it does possible and if you delete it, prepare to re-install Windows.
It is for another persons. They login to server thru this user to use their application by remote desktop connection. I eliminated this user thru an application and a secondary user & password . It works remotely fine,no body can inter into server environment, but if somebody comes to server room and uses console can control server. It seems i must use some services or write a script code to eliminate socondary user access to console.