Erasing unwanted accounts in my box

[lbrtchx@gmail.com]

I inherited a Windows computer that I have been using fine, but there
are a number of accounts that I would like to delete:
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1) ASPNET
2) Guest
3) Helpassistant
4) SUPPORT_388945a0
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While viewing these accounts under windows:
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http://www.geocities.com/tekmonk2005/pix/WindowsPW00.JPG
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http://www.geocities.com/tekmonk2005/pix/WindowsPW02_Users.JPG
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http://www.geocities.com/tekmonk2005/pix/WindowsPW04_Groups.JPG
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I noticed that even if the account RLopez belongs to the network
domain "EXCHANGE", it would successfully log in even if the computer
is not connected to any network at all
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I read online about busybox and I ran it on my box
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http://www.geocities.com/tekmonk2005/pix/BusyBox00_Dir2SAM.JPG
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http://www.geocities.com/tekmonk2005/pix/BusyBox02_PssWrdz.JPG
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I also ran busybox in other Windows boxes and they showed if the
account had admin rights or not, why doesn't this box show it?
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Also, what is this "dis/lock" thing that you can see?
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How can you those "ASPNET", "SUPPORT_388945a0", "helpassistant" and
"support" be totally removed from my computer?
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Any good and authoritative information about login accounts and file
based security for Windows and in general?
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Thanks
lbrtchx