Private Declare Function GetUserName Lib "advapi32.dll" Alias "GetUserNameA" (ByVal lpBuffer As String, nSize As Long) As Long

Private Sub Form_Load()
Dim ret As Long, UserName As String
Dim lpBuff As String * 25

ret = GetUserName(lpBuff, 25)
    UserName = Left(lpBuff, InStr(lpBuff, Chr(0)) - 1)
        List1.AddItem UserName
End Sub