Security issue, many old and archived users showing up as administrators

OS: XP Professional SP3


I really have annoying problems.

Here is the main problem, as for latter time my computer administrator
account was been hacked(has been locked out) by some viruses which
affects the logon part of the system and eventually i managed to fix
it and to get it out of my computer but still i'm not on opening with
that that computer is clean for sure...with "hundred!thousands of
registry files and with numerous possibilities i doubt it really is,
but i trust the paid antivirus a lot, + some checked recommended
programs.

What is odd is this list of Groups & users for which i don't know how
to maintain to change as it is for sure phony, but i don't know how to
manage it, from where to manage it and in which way is it in
connection with the security issues as i believe this is especially
important security question regarding one user Os.

This are local users and groups (for which i'm convinced that they are
on computer as i work through them and as an administrator of this
computer am convinced that there is no others, but....),
http://img97.imageshack.us/i/90027102.jpg/


Then on the other hand i have this list which is much in confrontation
with the local users and groups list;

http://img4.imageshack.us/i/usersandgroups2.jpg/
http://img862.imageshack.us/i/usersgroups1.jpg/


AllRight, i know what administrators are. what my personal
administrator account is, i also know the existance of SYSTEM, CREATOR
OWNER, Everyone, Backup operators but what the hell are all this other
groups and users when e.g. guests have been locked oout as a group.
etc.



Please explanations, links, whatever what could be handy !!!

I also am looking more good valid texts&explanations about everyone
group, system group and creator owner group,
e.g. what if everyone group has a 'full control' right on some of my
folders, is it reffering also on the remote control user, and what
full coontrol really is what is in difference from read-change
files...
e.g. in what kind of connection is SYsTEM, CREATOR OWNER profiles with
me as an administrator in administrator groups + built-in
administrator account ????