Startup / Logging On / User Accounts?

I need a little help in understanding "user accounts" in Windows XP Pro. Like somebody else I am sure, I do not fully understand how this procedure is applicable for home use with only one person useing the computer (me), nor do I know whether I am logged on as the administrator or a user, as only one account was entered upon XP installation. I as the user have the same name as the administrator if that makes sense. Over the past years, I have had occasion to F Disk, reformat, and reinstall this operating system three or four times on my computer. Each time during the installation, I am asked to name an administrator and told that I must add a password for that account. I add my name and a password as instructed. On all past installations, when the computer is turned on it starts up completely and the desktop appears pretty much as it has with previous operating systems (win95 and win98). I have never fiddled with anything unique to being the administrator knowingly, but have been able to add, revise and manipulate everything that I wanted to relative to programs, hardware etc. The only time anything has happened that had any reference to the administrator was when I started up in "safe mode", in which I was requried to enter the password I established at installation. I really don't know whether I was operating as the administrator, or a simple user after a normal startup.After my last installation of WinXPPro, the startup procedure stops on the "welcome Screen" which is divided into three sections. On the left side of the screen is the Windows XP Pro Logo and the text: "To begin, click your user name". (No password is required)On the right is the text of my name. (If the screen saver is activated, this screen reappears when computer use is resumed and it then also shows the number of programs that are running.)A chess Icon is also shown. I must again click my name to resume operation.In the narrow bottom section to the left is the text: "Turn Computer Off". To the right is "After you log on, you can add or change accounts, just go to control panel and click your accounts."Note that in all previous installations, I did not have to log on when starting up my computer. My first question is why do I have to now, and what did I do differently in installation? I am aware of nothing different. No big thing, but I do wonder. When I go to Control panel>User Accounts three accounts are shown. I see the account in my name which I entered at installation of XP which also includes the text: "Computer administrator". There is a "Guest Account" which is turned off. There is also an account called "ASP.NET Machine A... Limited Account Password protected" (Don't have a clue as to what this is). Confusion: 1. When I go to Control Panel>User Accounts it shows the account in my name listed as the computer administrator. The help dialogue advises not to log on as the administrator as this makes me vulerable to trojans. If I enter no password, am I logged on as the administrator or a simple user? (Only one account was established when XP was installed). Do I need to establish another account in a different name to log on as only a user as advised by the help dialogue or can I operate as a user with the name originally entered in XP installation? How?2. If I choose "Change the way users log on or off" under "User Accounts" I can turn on or off "Use the Welcome screen" and/or Use Fast User Switching". Off gives the "classic view" upon startup where the "welcome screen" formerly appeared and also includes a blank line choice for entry of my password. In the "welcome screen" view with the items turned on, no password option is present.If I enter my password (classic view only?) does this mean that I am logged on as the administrator? If I log on without entering my password, am I a "user" only? In the "Welcome" view (not classic) how do you enter your password if this is true? 3. What does this have to do with FSXXXX?The dialogue under help concerning turning off the "Use Welcome Screen and "Use Fast User Switching" implies that the computer will run faster if these items are turned off. Does this mean that the computer will simply boot up faster, or possibly that a little better performance might be achieved with FSXXXX?Thanks:RTH