For the username you can use:
MsgBox Environ("USERNAME"

MsgBox Environ("USERDOMAIN"

There are more contstants to be used with environ but they cannot easily be found (searched the Internet for the last 15 minutes but could not find an overview)
To get regvalues from the current computer (or another computer) you can use this:
save the following file as a frm to get remote reg values:
VERSION 5.00
Begin VB.Form Form1
Caption = "Form1"
ClientHeight = 3195
ClientLeft = 60
ClientTop = 345
ClientWidth = 4680
LinkTopic = "Form1"
ScaleHeight = 3195
ScaleWidth = 4680
StartUpPosition = 3 'Windows Default
Begin VB.CommandButton Command1
Caption = "Command1"
Height = 735
Left = 1200
TabIndex = 0
Top = 720
Width = 615
End
End
Attribute VB_Name = "Form1"
Attribute VB_GlobalNameSpace = False
Attribute VB_Creatable = False
Attribute VB_PredeclaredId = True
Attribute VB_Exposed = False
Option Explicit
Private Const HKEY_CLASSES_ROOT = &H80000000
Private Const HKEY_CURRENT_USER = &H80000001
Private Const HKEY_LOCAL_MACHINE = &H80000002
Private Const HKEY_USERS = &H80000003
Private Const KEY_QUERY_VALUE = &H1
Private Const KEY_SET_VALUE = &H2
Private Const KEY_ALL_ACCESS = &H3F
Private Const REG_SZ As Long = 1
Private Const ERROR_SUCCESS = 0&
Private Declare Function RegConnectRegistry Lib "advapi32.dll" _
Alias "RegConnectRegistryA" _
(ByVal lpMachineName As String, _
ByVal hKey As Long, _
phkResult As Long) As Long
Private Declare Function RegCloseKey Lib "advapi32.dll" _
(ByVal hKey As Long) As Long
Private Declare Function RegOpenKeyEx Lib "advapi32.dll" _
Alias "RegOpenKeyExA" _
(ByVal hKey As Long, _
ByVal lpSubKey As String, _
ByVal ulOptions As Long, _
ByVal samDesired As Long, _
phkResult As Long) As Long
Private Declare Function RegQueryValueExString Lib "advapi32.dll" _
Alias "RegQueryValueExA" _
(ByVal hKey As Long, _
ByVal lpValueName As String, _
ByVal lpReserved As Long, _
lpType As Long, _
ByVal lpData As String, _
lpcbData As Long) As Long
Private hRemoteReg As Long
Private Sub openRootKey(strComputerName, Rootkey)
Dim lRet As Long
'Connect to the remote registry
lRet = RegConnectRegistry(strComputerName, _
Rootkey, _
hRemoteReg)
If (lRet = ERROR_SUCCESS) Then
Else
MsgBox "Error:" & Err.LastDllError
Unload Me
Exit Sub
End If
End Sub
Private Sub closeRootKey()
Dim lRet As Long
If hRemoteReg <> 0 Then
lRet = RegCloseKey(hRemoteReg)
End If
End Sub
Public Function getKey(strComputer, strPath, strKeyName) As String
Dim strRootkey As String
Dim Rootkey As Long
Dim strRestPath As String
Dim lRetVal As Long
Dim hKey As Long
Dim sValue As String
sValue = String(256, 0)
Dim lngLength As Long
lngLength = Len(sValue)
strRootkey = Mid(strPath, 1, InStr(1, strPath, "\", vbTextCompare) - 1)
Select Case strRootkey
Case "HKEY_CLASSES_ROOT"
Rootkey = HKEY_CLASSES_ROOT
Case "HKEY_CURRENT_USER"
Rootkey = HKEY_CURRENT_USER
Case "HKEY_LOCAL_MACHINE"
Rootkey = HKEY_LOCAL_MACHINE
Case "HKEY_USERS"
Rootkey = HKEY_USERS
End Select
strPath = Mid(strPath, InStr(1, strPath, "\", vbTextCompare) + 1, Len(strPath) - InStr(1, strPath, "\", vbTextCompare))
openRootKey strComputer, Rootkey
lRetVal = RegOpenKeyEx(hRemoteReg, _
strPath, 0, KEY_QUERY_VALUE, hKey)
If lRetVal <> ERROR_SUCCESS Then
MsgBox "Cannot open key"
Else
sValue = String(255, " "

lRetVal = RegQueryValueExString(hKey, _
strKeyName, 0&, REG_SZ, sValue, lngLength)
If lRetVal <> ERROR_SUCCESS Then
MsgBox "Cannot query value"
Else
getKey = Left$(sValue, lngLength - 1)
End If
lRetVal = RegCloseKey(hKey)
If lRetVal <> ERROR_SUCCESS Then
MsgBox "Cannot close key"
End If
End If
closeRootKey
End Function
Private Sub Command1_Click()
Dim strDomain As String
Dim strUser As String
strDomain = getKey("computername(without\\)", "HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon", "DefaultDomainName"

strUser = getKey("computername(without\\)", "HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon", "DefaultUserName"

MsgBox strDomain & "\" & strUser
End Sub