I've had my notebook pc--which runs Windows XP Professional--for half a year
and always just had the one "Administrator" account since I'm the only user.  
Recently, I learned about multiple accounts and yesterday set up a second,
"limited" account under my name, Bill.  This morning I turned on my pc and
there is no user "Administrator" listed at the log on screen, just my limited
Bill user account.  Thus, I CAN NOT GET TO ANY OF MY WORK FILES FOR THE PAST
SIX MONTHS.  How can I log on as the "Administrator" again?