сдлеть чтобы по двойному клику этот запускалась твоя программа и открывала этот файл

FileName=command$

dim FileName as string

public FileName as string

1. "Крутейшая" программа должна обрабатывать командную строку,
а именно брать оттуда путь и имя этого файла...
2. Смотрим, а не висит ли уже кто-либо на этом типе файлов....
Раздел [HKEY_CLASSES_ROOT\.ext], параметр [по умолчанию]
Пример: tmpStr = GetKeyValue(HKEY_CLASSES_ROOT, FileExt, ""
(Здесь FileExt - строковая константа, см. полный пример...)
Если никого нет, то tmpStr будет равно "".
3. Если никого нет, то создаем свой раздел DefaultReg, если кто-то уже
прицепился, то добавляем в его раздел (то есть в tmpStr).
Далее смотри код примера... Я даже комментариев понаписал...
(сколько смог...)
Полный пример (VB Код):

'Комментарии излишни по-моему...
Private FullPathAndFileName As String
Private CmdLine As String
'Определяет делать ли вообще то о чем идет речь...
Private Const UpdReg As Boolean = True
'Определяет ставить наше действие "по умолчанию" или нет...
Private Const UpdDefault As Boolean = True
'Расширение на которое подвешиваем свою программу...
Private Const FileExt As String = ".rom"
'Имя своего раздела в реестре если на этом типе файлов еще никто не висит...
'(само имя ни на что не влияет)
Private Const DefaultReg As String = "ROMfile"
'Действие, которое будем делать над файлом
Private Const DefaultAct As String = "Convert"
'Название действия, которое будем делать над файлом
'(Проводник именно эту надпись выведет по правой кнопке)
Private Const DefaultActName As String = "Преобразовать"
'Описание файлов с таким расширением...
Private Const ExtDescription As String = "Asm Output file"
'Я это ставлю на Form_Load....
Private Sub Form_Load()
Dim tmpStr As String
'Определяем свой путь и имя файла
FullPathAndFileName = App.Path
If Right(App.Path,1) <> "\" Then FullPathAndFileName = FullPathAndFileName & "\"
FullPathAndFileName = FullPathAndFileName & App.EXEName & ".exe %1"

If UpdReg Then'А надо ли в реестр-то писать? [const]

'Считываем на предмет "висит" ли кто на этом типе файлов...
tmpStr = GetKeyValue(HKEY_CLASSES_ROOT, FileExt, ""
If tmpStr = "" Then'Если никто не висит...
tmpStr = DefaultReg
'Делаем свою запись на это расширение
UpdateKey HKEY_CLASSES_ROOT, FileExt, "", tmpStr
'Присобачиваем свое описание таких файлов...
UpdateKey HKEY_CLASSES_ROOT, tmpStr, "", ExtDescription
End If
If UpdDefault Then
'Ставим свое действие "по умолчанию"
UpdateKey HKEY_CLASSES_ROOT, tmpStr & "\shell", "", DefaultAct
End If
'Прописываем название действия
UpdateKey HKEY_CLASSES_ROOT, tmpStr & "\shell\" & DefaultAct, "", DefaultActName
'Прописываем пути и имя нашей программы....
UpdateKey HKEY_CLASSES_ROOT, tmpStr & "\shell\" & DefaultAct & "\command", "", FullPathAndFileName
End If
'И пошла командная строка...
CmdLine = Command
CmdLine = Trim(CmdLine)

tmpStr = GetKeyValue(HKEY_CLASSES_ROOT, FileExt, ""

В реестре прописываешь open на твой тип вида PROGRAM.EXE %1 и наслаждаешься...

ЗЫ: Надеюсь не очень запутанно?

…\Program Files\Microsoft Visual Studio\Common\Tools\APE\REGTOOL5.DLL

Option Explicit


Public Declare Function RegOpenKeyEx Lib "advapi32" Alias "RegOpenKeyExA" (ByVal hKey As Long, ByVal lpSubKey As String, ByVal dwReserved As Long, ByVal samDesired As Long, phkResult As Long) As Long
Public Declare Function RegCreateKey Lib "ADVAPI32.dll" Alias "RegCreateKeyA" (ByVal hKey As Long, ByVal lpSubKey As String, phkResult As Long) As Long
Public Declare Function RegCloseKey& Lib "advapi32" (ByVal hKey As Long)
Public Declare Function RegQueryValueEx Lib "advapi32" Alias "RegQueryValueExA" (ByVal hKey As Long, ByVal lpValueName As String, lpReserved As Long, lpType As Long, lpData As Any, lpcbData As Long) As Long
Public Declare Function RegQueryInfoKey Lib "ADVAPI32.dll" Alias "RegQueryInfoKeyA" (ByVal hKey As Long, ByVal lpClass As String, lpcbClass As Long, ByVal lpReserved As Long, lpcSubKeys As Long, lpcbMaxSubKeyLen As Long, lpcbMaxClassLen As Long, lpcValues As Long, lpcbMaxValueNameLen As Long, lpcbMaxValueLen As Long, lpcbSecurityDescriptor As Long, lpftLastWriteTime As Any) As Long
Public Declare Function RegSetValueEx Lib "ADVAPI32.dll" Alias "RegSetValueExA" (ByVal hKey As Long, ByVal lpValueName As String, ByVal Reserved As Long, ByVal dwType As Long, lpData As Any, ByVal cbData As Long) As Long
Public Declare Function RegEnumKeyEx Lib "ADVAPI32.dll" Alias "RegEnumKeyExA" (ByVal hKey As Long, ByVal dwIndex As Long, ByVal lpName As String, lpcbName As Long, ByVal lpReserved As Long, ByVal lpClass As String, lpcbClass As Long, lpftLastWriteTime As Any) As Long
Public Declare Function RegEnumValue Lib "ADVAPI32.dll" Alias "RegEnumValueA" (ByVal hKey As Long, ByVal dwIndex As Long, ByVal lpValueName As String, lpcbValueName As Long, ByVal lpReserved As Long, lpType As Long, lpData As Any, lpcbData As Long) As Long
Public Declare Function RegDeleteKey Lib "ADVAPI32.dll" Alias "RegDeleteKeyA" (ByVal hKey As Long, ByVal lpSubKey As String) As Long
Public Declare Function RegDeleteValue Lib "ADVAPI32.dll" Alias "RegDeleteValueA" (ByVal hKey As Long, ByVal lpValueName As String) As Long

Private Const KEY_ALL_ACCESS            As Long = ((&H1F0000 Or &H1 Or &H2 Or &H4 Or &H8 Or &H10 Or &H20) And (Not &H100000))
Private Const REG_SZ                    As Long = &H1
Private Const REG_DWORD                 As Long = &H4
Private Const ERROR_SUCCESS             As Long = &H0

Public Enum RootKey
    HKEY_CLASSES_ROOT = &H80000000
    HKEY_CURRENT_USER = &H80000001
    HKEY_LOCAL_MACHINE = &H80000002
    HKEY_USERS = &H80000003
End Enum

Public Function RegGetValue(hKey As RootKey, strSubKey As String, strValueName As String) As String
    Dim lngDataLen As Long, hSubKey As Long, strSetting As String
    If RegOpenKeyEx(hKey, strSubKey, 0, KEY_ALL_ACCESS, hSubKey) = ERROR_SUCCESS Then
        strSetting = Space(255): lngDataLen = Len(strSetting)
        If RegQueryValueEx(hSubKey, strValueName, ByVal 0, REG_SZ, ByVal strSetting, lngDataLen) = ERROR_SUCCESS Then
            If lngDataLen > 1 Then RegGetValue = Left(strSetting, lngDataLen - 1)
        End If
        RegCloseKey hSubKey
    End If
End Function

Public Sub RegSetValue(hKey As RootKey, strSubKey As String, strKey As String, strValue As String)
    Dim keyhand As Long
    Call Trim(strKey): Call Trim(strValue)   'Убираем пробелы в нач. и кон. строки
    If Len(strKey) = 0 Or Len(strValue) = 0 Then Exit Sub

    Call RegCreateKey(hKey, strSubKey, keyhand)
    Call RegSetValueEx(keyhand, strKey, 0, 1&, ByVal strValue, Len(strValue) + 1)
    Call RegCloseKey(keyhand)
End Sub

Public Sub RegSetKey(hKey As RootKey, strSubKey As String)
    Dim keyhand As Long
    RegCreateKey hKey, strSubKey, keyhand
    RegCloseKey keyhand
End Sub

Public Function RegGetDWord(hKey As RootKey, strSubKey As String, strValueName As String) As Long
    Dim hSubKey As Long, lngRetVal As Long
    If RegOpenKeyEx(hKey, strSubKey, 0, KEY_ALL_ACCESS, hSubKey) = ERROR_SUCCESS Then
        If RegQueryValueEx(hSubKey, strValueName, ByVal 0, REG_DWORD, lngRetVal, 4) = ERROR_SUCCESS Then RegGetDWord = lngRetVal
        RegCloseKey hSubKey
    End If
End Function

Public Sub RegSetDWord(hKey As RootKey, strSubKey As String, strValueName As String, lngData As Long)
    Dim hNewHandle As Long
    RegCreateKey hKey, strSubKey, hNewHandle
    RegSetValueEx hNewHandle, strValueName, 0, REG_DWORD, lngData, 4
    RegCloseKey hNewHandle
End Sub

Public Function RegGetKeys(hKey As RootKey, strSubKey As String, strRetArray() As String, Optional Range As Long) As Long
    Dim hChildKey As Long, lngSubKeys As Long, lngMaxKeySize As Long, lngDataRetBytes As Long, i As Integer
    If Len(strSubKey) Then
        If RegOpenKeyEx(hKey, strSubKey, 0, KEY_ALL_ACCESS, hChildKey) <> ERROR_SUCCESS Then Range = -1: Erase strRetArray: Exit Function
    Else
        hChildKey = hKey
    End If
    If QueryRegInfoKey(hChildKey, lngSubKeys, lngMaxKeySize) <> ERROR_SUCCESS Or lngSubKeys = 0 Then
        If Len(strSubKey) Then RegCloseKey hChildKey
        Range = -1
        Erase strRetArray
        Exit Function
    End If
    lngSubKeys = lngSubKeys - 1
    ReDim strRetArray(lngSubKeys) As String
    For i = 0 To lngSubKeys
        lngDataRetBytes = lngMaxKeySize
        strRetArray(i) = Space(lngMaxKeySize)
        RegEnumKeyEx hChildKey, i, strRetArray(i), lngDataRetBytes, 0&, vbNullString, ByVal 0&, ByVal 0&
        strRetArray(i) = Left(strRetArray(i), lngDataRetBytes)
    Next i
    If Len(strSubKey) Then RegCloseKey hChildKey
    Range = lngSubKeys
    RegGetKeys = lngSubKeys
End Function

Public Function RegGetKeyValues(hKey As RootKey, strSubKey As String, strValues() As String, Optional Range As Long) As Long
    Dim lngMaxValSize  As Long, lngValRetBytes As Long, lngMaxSettingSize As Long, lngSetRetBytes As Long
    Dim lngSetting As Long, lngType As Long, hChildKey As Long, i As Integer, lngNumValues As Long

    If RegOpenKeyEx(hKey, strSubKey, 0, KEY_ALL_ACCESS, hChildKey) <> ERROR_SUCCESS Then Range = -1: Erase strValues: Exit Function
    If QueryRegInfoKey(hChildKey, , , lngNumValues, lngMaxValSize, lngMaxSettingSize) <> ERROR_SUCCESS Or lngNumValues = 0 Then RegCloseKey hChildKey: Erase strValues: Exit Function

    lngNumValues = lngNumValues - 1
    ReDim strValues(0 To lngNumValues, 0 To 1) As String
    For i = 0 To lngNumValues
        strValues(i, 0) = Space(lngMaxValSize): lngValRetBytes = lngMaxValSize: strValues(i, 1) = Space(lngMaxSettingSize)
        lngSetRetBytes = lngMaxSettingSize

        RegEnumValue hChildKey, i, strValues(i, 0), lngValRetBytes, 0, lngType, ByVal strValues(i, 1), lngSetRetBytes
        If lngType = REG_SZ Then
            strValues(i, 1) = Left(strValues(i, 1), lngSetRetBytes - 1)
        ElseIf lngType = REG_DWORD Then
            lngValRetBytes = lngValRetBytes + 1
            RegEnumValue hChildKey, i, strValues(i, 0), _
                lngValRetBytes, 0, lngType, lngSetting, lngSetRetBytes
            strValues(i, 1) = CStr(lngSetting)
        Else
            strValues(i, 1) = vbNullString
        End If
        strValues(i, 0) = RTrim(Left(strValues(i, 0), lngValRetBytes))
        strValues(i, 1) = RTrim(strValues(i, 1))
    Next i
    RegCloseKey hChildKey
    Range = lngNumValues
    RegGetKeyValues = lngNumValues
End Function

Private Function QueryRegInfoKey(hKey As RootKey, Optional lngSubKeys As Long, Optional lngMaxKeyLen As Long, Optional lngValues As Long, Optional lngMaxValNameLen As Long, Optional lngMaxValLen As Long)
    QueryRegInfoKey = RegQueryInfoKey(hKey, vbNullString, ByVal 0&, 0&, lngSubKeys, lngMaxKeyLen, ByVal 0&, lngValues, lngMaxValNameLen, lngMaxValLen, ByVal 0&, ByVal 0&
    lngMaxKeyLen = lngMaxKeyLen + 1
    lngMaxValNameLen = lngMaxValNameLen + 1
    lngMaxValLen = lngMaxValLen + 1
End Function



Public Sub RegDelKey(hKey As RootKey, strKeyToDel As String)
    RegDeleteKey hKey, strKeyToDel
End Sub

Public Sub RegDelValue(hKey As RootKey, strSubKey As String, strValToDel As String)
    Dim hSubKey As Long
    RegOpenKeyEx hKey, strSubKey, 0, KEY_ALL_ACCESS, hSubKey
    RegDeleteValue hSubKey, strValToDel
    RegCloseKey hSubKey
End Sub

'Копирование стринговых значений из 1-го ключа в другой
'Public Sub CopyKeyVal(hKey As RootKey, sFrom As String, sTo As String)
'    im sArray() As String, ii As Long
'    Call RegGetKeyValues(HKEY_LOCAL_MACHINE, sFrom, sArray)
'    For ii = 0 To UBoundS(sArray)
'        Call RegSetValue(HKEY_LOCAL_MACHINE, sTo, sArray(ii, 0), sArray(ii, 1))
'    Next
'End Sub