I do have experience with XP Home.  XP Home lacks a number of things that XP
Pro has and it certainly can be confusing.  :-)

No.  The Power Users group doesn't exist on WINDOWS XP Home Edition.

No.  Local Users and Groups will popup an error in XP Home.

Yes.  This can be confusing, if you have XP Home.  Maybe even if you do not
have XP Home.  ;-)

On a stand alone machine, with XP Home.
control userpasswords2 Brings up User Accounts, the one you would get from
My Computer | Manage | Local Users and Groups.

And this is what you'll get when you try to access...

[[The userpasswords2 applet should not be used on WINDOWS XP Home Edition as
a tool to edit or modify users.  It is reserved for WINDOWS XP Professional
Edition. The reason for this is that userpasswords2 allows the user to
access to the 'Power Users' group which doesn't exist on WINDOWS XP Home
Edition.]]

If you try to access Local Users and Groups (Local) with XP Home, you will
get...

[[This computer is running Windows XP Home Edition.  This snapin may not be
used with that version of Windows.  To manage user accounts for this
computer, use the User Accounts tool in the Control Panel]]

control userpasswords is what should be used with XP Home, *not* control
userpasswords2!

Power Users group are not supported by WinXP Home, so one should not try to
assign such privileges to an existing account, or else errors will appear.
Such as:

[[The user could not be added because the following error has occurred, The
group name could not be found: When creating a new user and make it member
of the 'Power Users' group.]]

[[The group membership for <ComputerName\UserName> could not be updated :
When updating an existing user, adding him to the 'Power Users group'. ]]

Local Users and Groups overview
[[Local Users and Groups is a tool you can use to manage local users and
groups. It is available on the following operating systems:
Windows 2000 Professional
Windows XP Professional
Member servers running Windows 2000 Server]]

Local Users and Groups overview
http://www.microsoft.com/resources/documentation/windows/xp/all/proddocs/en-us/l
sm_overview_01.mspx

This is KB817365 which for some reason has been pulled from MS-KB.
Although I have a copy and this is the same as KB817365.
Creation of user in the 'Power Users' group with 'Control Userpasswords2'
http://www.it-faq.pl/mskb/817/365.HTM

13. Advanced User Management in Windows XP Home
http://snakefoot.fateback.com/tweak/winnt/usermgt.html#USERPASSWORDS2

It is so like Microsoft to name things similarly.  Just to confuse people,
IMHO.
control userpasswords = User Accounts
control userpasswords2 = User Accounts
But they are *not* the same.

If you want to be a member of the Power Users group, get Windows XP
Professional.