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CFormatDriveDialog - A wrapper class for the undocumented SHFormatDrive API function

, 27 Aug 2002
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A wrapper class for SHFormatDrive (XP/2K only). Corrects some errors in KB article Q173688


This class basically brings up the Windows Disk-Format dialog box. You'd have thought it would have become part of the common dialogs by now. What's worse is that some of the information in KB article Q173688 is now incorrect as far as Windows XP and Windows 2000 are concerned. I presume that the KB article was written during the 9x days and they forgot to remove or update it later. What confused me was that the KB article  states that the information in it applies to XP and 2K. The first shock for me was to discover that the Quick-Format option behaved exactly opposite to how it was described in the KB article. In addition the Make-system-disk option was not even working properly. Anyway I've written a class - CFormatDriveDialog that basically wraps the stuff for you. I have stuck to the MS recommended constant definitions where they work, but in other cases I've either discarded them or added my own.

Strong warning

The information in KB article Q173688 is partially incorrect. Do not follow it blindly if you intend to build on this class. Also note that this class should only be used on Win2K/XP systems. The KB article is to be followed for older OS versions like 9x and ME.

Class Reference

There's just one public method here (of course, in addition to the parameter-less constructor).


int CFormatDriveDialog::DoModal(HWND hWnd, UINT Drive, bool bQuickFormat, LPCTSTR vol_label);

  • hWnd - The window handle of the dialog's parent. This cannot be NULL.
  • Drive - The drive code (0 for A, 1 for B, 2 for C etc.) I've defined constants like DRIVEA, DRIVEB, DRIVEC etc. which you may use instead of raw numbers. They are defined in the header file.
  • bQuickFormat - If true then the Quick-Format check box is ticked by default.
  • vol_label - The default value for the volume label to be used.

Return Value

IDOK if a successful format was completed and IDCANCEL if the format operation was cancelled or if some error occurred.

Sample Usage

void Cnish_testDlg::OnBnClickedButton1()
    CFormatDriveDialog dlg;
    int d=dlg.DoModal(AfxGetMainWnd()->m_hWnd,DRIVEA,

Tech Details

We call the SHFormatDrive function from shell32.dll. I use LoadLibrary and load shell32.dll and then call GetProcAddress to get SHFormatDrive's address. I also use SetWindowsHookEx to set a CBT hook because we need to set the volume label. The hook proc calls EnumChildWindows and when we encounter a child window with "Edit" class, we know this is the volume label edit box, because that's the only edit box in the dialog. Refer the source code for full details. A snipped partial listing is given below with comments not found in the actual source code.

int CFormatDriveDialog::DoModal(...)


    // Function pointer to hold SHFormatDrive
    FMTDRIVEFUNC* pshfd;

    // Load the dll
    HMODULE hMod = LoadLibrary("shell32.dll");

    // Chk for error - just in case
        // Assign function pointer
        pshfd = reinterpret_cast<FMTDRIVEFUNC*>

        // Set a WH_CBT hook
        m_hHook = SetWindowsHookEx(WH_CBT,CBTProc,

        // Call the function via the function pointer
        rv = ((*pshfd)(hWnd,Drive,SHFMT_ID_DEFAULT,Options)==

        // Free the dll

LRESULT CALLBACK CFormatDriveDialog::CBTProc(...)
    if (nCode == HCBT_ACTIVATE )
        // Get handle of Format dialog
        HWND hWnd = reinterpret_cast<HWND>(wParam);

        // Enumerate all child windows to get 
        // volume label the edit box

        // Finished our need for the hook
        CFormatDriveDialog::m_hHook = NULL; 
    return FALSE;

BOOL CALLBACK CFormatDriveDialog::EnumChildProc(...)
    char buff[256];

    // The vol label edit box is the only edit control
        return FALSE;
    return TRUE;


There are several return codes and option codes mentioned in the above mentioned KB article. But none of them work as expected, and some of them don't work at all. In addition the code constant given for Quick-Format works in the exact opposite manner. Of course I base my results from trying out the code on my own machine which is an XP professional box. I also got James T Johnson to test it partially on his XP professional box and Smitha(Tweety) to test it on her Windows 2000 professional box. But I have no idea how this class will work on untested OS versions with or without service packs.


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About the Author

Nish Nishant

United States United States
Nish is a real nice guy who has been writing code since 1990 when he first got his hands on an 8088 with 640 KB RAM. Originally from sunny Trivandrum in India, he has been living in various places over the past few years and often thinks it’s time he settled down somewhere.
Nish has been a Microsoft Visual C++ MVP since October, 2002 - awfully nice of Microsoft, he thinks. He maintains an MVP tips and tricks web site - where you can find a consolidated list of his articles, writings and ideas on VC++, MFC, .NET and C++/CLI. Oh, and you might want to check out his blog on C++/CLI, MFC, .NET and a lot of other stuff -
Nish loves reading Science Fiction, P G Wodehouse and Agatha Christie, and also fancies himself to be a decent writer of sorts. He has authored a romantic comedy Summer Love and Some more Cricket as well as a programming book – Extending MFC applications with the .NET Framework.
Nish's latest book C++/CLI in Action published by Manning Publications is now available for purchase. You can read more about the book on his blog.
Despite his wife's attempts to get him into cooking, his best effort so far has been a badly done omelette. Some day, he hopes to be a good cook, and to cook a tasty dinner for his wife.

Comments and Discussions

GeneralVista problem PinmemberKranggg22-Oct-09 11:25 
Generala problem Pinmemberqiqi552125-Dec-08 16:45 
Generalhi Pinmemberqiqi552123-Dec-08 18:07 
Generalthe bigger the disk space , the greater the effect. Pinmemberqiqi552123-Dec-08 20:15 
GeneralUmounting the drive Pinmemberjoelparker2-Apr-04 7:45 
Generalformat disk without dialog Pinmemberpoganka24-Jan-04 22:20 
GeneralRe: format disk without dialog Pinmemberzbilal12-Mar-04 13:00 
GeneralRe: format disk without dialog ( How can I do .. ) Pinmemberka.kevinliu29-Mar-07 21:09 
GeneralRe: format disk without dialog ( How can I do .. ) PinmemberGeorge Grimes6-Apr-07 19:22 
GeneralDialog Pinmemberjlechem14-May-03 7:05 
GeneralNot a graphic interface and Hi Rating!!! Great!!! PinmemberGabriel 229-Aug-02 10:29 
GeneralRe: Not a graphic interface and Hi Rating!!! Great!!! PineditorNishant S29-Aug-02 15:03 
GeneralVery good article PinmemberMatt Newman29-Aug-02 5:05 
GeneralRe: Very good article PineditorNishant S29-Aug-02 15:03 
GeneralGood work PinmemberKannan Kalyanaraman28-Aug-02 21:38 
Keep up the good work.
Nish, probably you should write a tutorial for cbt hooks.
I didnt look up CP articles for that one ... Unsure | :~
GeneralRe: Good work PineditorNishant S28-Aug-02 21:45 
GeneralIt Is Documented PinmemberBlake Coverett28-Aug-02 13:27 
GeneralRe: It Is Documented PineditorNishant S28-Aug-02 13:34 
GeneralRe: It Is Documented #2 PineditorNishant S28-Aug-02 13:38 
QuestionCan you PinmemberChris Losinger28-Aug-02 7:11 
AnswerRe: Can you PinmemberJörgen Sigvardsson28-Aug-02 8:25 
GeneralRe: Can you PinmemberChris Losinger28-Aug-02 8:38 
AnswerRe: Can you PineditorNishant S28-Aug-02 12:51 
GeneralRe: Can you PinmemberChris Losinger28-Aug-02 12:49 
GeneralRe: Can you PinsussAnonymous29-Aug-02 21:02 

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