I use Windows XP Pro.  Last night I tried to create a new user profile
and logon name for my computer.  I also activated the guest account. 
After restarting the computer I now can't access my administrator
account.  I seem to be able to switch between the new user account and
the guest account, but cannot select my administrator account.  I
don't believe I turned off or deleted my administrator account (could
I have?)  I have tried to go to the "user accounts" in the control
panel, but it doesn't appear to give me an option to select the
administrator account.

How can I access my administrator account?

Hi danmn, the account named "administrator" is not for general use. It
is for troubleshooting purpose. As soon as you have made another
administrator account the default administrator account has been
hidden. Its only viewable in safe mode. You should use your new
administrator account from now. If you believe that you have urgent
need of that account or in case you cannot shift to the new, you can
make that listed under welcome screen by a registry modification. You
can do it manually or just run a script available from this site
http://www.kellys-korner-xp.com/xp_tweaks.htm
Click on "Enable/Disable Administrator on Welcome Screen" at the right
column 5th line.

Thank you.

Great, that seemed to work well.  I would have continued using the new
user I made, but it didn't seem to have access (or at least not
apparent access) to all my old files and programs.  Any idea how I
would have accessed these files from the new account?

Thanks for the previous answer!!  How do I give you the fee?

You can also go to Control Panel, User Accounts, "Change the way users
log on or off", uncheck "use the welcome screen".  You then are
required to enter your un and pass manually, simply login with
"administrator" and whatever password you created, or blank if you
never set one up.  This avoids reg hacks.

All the info for your admin account will be under c:\documents and
settings\administrator.  You can copy what you want to your other
profile, or create a directory on c:, copy to there, then login with
other profile and copy back.  Hope this helps.

Many thanks!

You don't need to uncheck "use the welcome screen". Just press
CTRL+ALT+DEL twice to get access to the normal login page.
Probably the new user profile you created is not an administrator,
thats why you cant have access to your old files.
One more thing, I dont like to use the guest account, its better to
create a user with no administrative privileges instead.
Have I been clear?

Yours, 
Vlad

Press Alt+Ctrl+Del Twice.

Enter your username (i.e. administrator) and password :)