Writing From HKEY_USERS - windows

Question

I am attempting to create an application that will allow me to input a username and switch that user's default printer by modifying the registry under HKEY_USERS\UserSID. I cannot seem write values to that section of the registry though. Perhaps it's a Windows limitation? Here's the code I have so far.
Dim strComputer = "."
Dim objWMIService As Object = GetObject("winmgmts:\\" & strComputer & "\root\cimv2")
Dim theUsername As String = TextBox1.Text
Dim theDomain As String = TextBox2.Text
Dim objAccount As Object = objWMIService.Get("Win32_UserAccount.Name='" & theUsername & "',Domain='" & theDomain & "'")
Dim theport As RegistryKey
theport = Registry.CurrentUser.OpenSubKey("Software\\Microsoft\\Windows NT\\CurrentVersion\\Devices")
Dim val As Object = theport.GetValue(ListBox1.SelectedItem)
theport.Close()
Dim theSid As String = objAccount.sid
Dim theKey As RegistryKey = Registry.Users.OpenSubKey(theSid + "\\Software\\Microsoft\\Windows NT\\CurrentVersion\\Windows", True)

Answer 1

I don't think that there is some Windows limitation, because I wrote to HKEY_USERS\SIDs many times. But I used for this purpose the vbscript. Also I should warn you that you can only read&write to Users registry if they are logged. For not logged users - use the ActiveSetup.
There is my script on vbs which writes some registry to all logged users. Hope you could adapt it to VB.NET.
Option Explicit
Const HKEY_USERS = &H80000003
Dim objReg, objWMI, colSessions, objSession, colList, colUsers, objUser, Domain, UserName, objUserAccount, SID, WshShell
Set WshShell = CreateObject("WScript.Shell")
Set objReg = GetObject("winmgmts:{impersonationLevel=impersonate}!\\.\root\default:StdRegProv")
Set objWMI = GetObject("winmgmts:{impersonationLevel=impersonate}!\\.\root\cimv2")
Set colSessions = objWMI.ExecQuery("Select * from Win32_LogonSession Where LogonType = 2 Or LogonType = 10")
If colSessions.Count <> 0 Then
For Each objSession in colSessions
Set colUsers = objWMI.ExecQuery("Associators of " & "{Win32_LogonSession.LogonId=" & objSession.LogonId & "} " & "Where AssocClass=Win32_LoggedOnUser Role=Dependent" )
For Each objUser in colUsers
Domain = objUser.Domain : UserName = objUser.Name
Set objUserAccount = GetObject("winmgmts:{impersonationLevel=impersonate}!\\.\root\cimv2:Win32_UserAccount.Domain='" & Domain & "',Name='" & UserName & "'")
SID = objUserAccount.SID
objReg.CreateKey HKEY_USERS, SID & "\Control Panel\Desktop"
objReg.SetStringValue HKEY_USERS, SID & "\Control Panel\Desktop", "Example", "1"
objReg.SetDwordValue HKEY_USERS, SID & "\Control Panel\Desktop", "Example", "2"
Next
Next
End If