You know, through, you can have accounts for multiple PC users.
But, if you don't want someone sees your account, what then?
Right, making a hidden account!
The most known account is called, Administrator, but not accessable in XP Home.
All other hidden accounts are accessable. ;)

Press Super+E to start Windows Explorer.
Click Control Panel (or however it's called) and doubleclick Useraccounts.
And create a user account like usual.
Let's call it, "secret"

Here it is. :3

Now press Super+R to Run a command.
Typ in Regedit (or Regedit.exe).
Go to: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\WindowsNT\CurrentVersion\Winlogon\SpecialAccounts\UserList
And right click on an empty space (New -> DWORD).
Give it exact the same name as you did in the Control Panel.
And set the worth on 0 (it's mostely 0 on default).

You don't see it!
Let's log off and be sure nobody else is logged in.
Press CTRL+Alt+Delete twince, so you'll have a classic logon screen.
And login as "secret".

And here you have it! :D

It's not that hard.
Remember, you can pwn the owner of the computer. ;P