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How to enumerate logical drives in the system?

To find out what drives are in the system and of what kind, you need three functions: GetLogicalDriveStrings() or GetLogicalDrives and GetDriveType(). I've borrowed the sample from MSDN Magazine:

 ////////////////////////////////////////////////////////////////
// MSDN Magazine -- April 2002
// If this code works, it was written by Paul DiLascia.
// If not, I don't know who wrote it.
// Compiles with Visual C++ 6.0. Set tabsize = 3 in your editor.
// Runs in Windows XP and probably Windows 2000 too.
//
#include "stdafx.h"
#include "resource.h"

#ifdef _DEBUG
#define new DEBUG_NEW
#undef THIS_FILE
static char THIS_FILE[] = __FILE__;
#endif

using namespace std; // for string class

//////////////////
// This mini-table maps GetDriveType codes to human-readable string
//
struct {
	UINT type;			// return code from GetDriveType
	LPCSTR name;		// ascii name
} DriveTypeFlags [] = {
	{ DRIVE_UNKNOWN,     "Unknown" },
	{ DRIVE_NO_ROOT_DIR, "Invalid path" },
	{ DRIVE_REMOVABLE,   "Removable" },
	{ DRIVE_FIXED,       "Fixed" },
	{ DRIVE_REMOTE,      "Network drive" },
	{ DRIVE_CDROM,       "CD-ROM" },
	{ DRIVE_RAMDISK,     "RAM disk" },
	{ 0, NULL},
};

//////////////////
// Standard tmain for MFC ListDrives app
//
int _tmain(int argc, TCHAR* argv[], TCHAR* envp[])
{
	if (!AfxWinInit(::GetModuleHandle(NULL), NULL, ::GetCommandLine(), 0)) {
		cerr << _T("Fatal Error: MFC initialization failed") << endl;
		return -1;
	}

	// Get logical drive strings-- a:\b:\c:\... etc.
	// Could also use GetLogicalDrives to get in the form of a bitmap instead
	// of character string.
	//
	TCHAR buf[100];
	DWORD len = GetLogicalDriveStrings(sizeof(buf)/sizeof(TCHAR),buf);

	// Display information about each drive.
	//
	string msg = "Logical Drives:\n";  // STL string
	for (TCHAR* s=buf; *s; s+=_tcslen(s)+1) {
		LPCTSTR sDrivePath = s;
		msg += sDrivePath;
		msg += " ";

		// GetDriveType gets one of the enum values DRIVE_UNKNOWN, etc.
		//
		UINT uDriveType = GetDriveType(sDrivePath);

		// Find drive type in table. I do a table lookup here to be extra
		// cautious, but since the uDriveType values are sequential, i could've
		// used DriveTypeFlags[uDriveType] instead of linear lookup. In
		// practice you would usually perform some check like
		//
		//	if (uDriveType & DEVICE_CDROM) {
		//		...
		//	}
		//
		for (int i=0; DriveTypeFlags[i].name; i++) {
			if (uDriveType == DriveTypeFlags[i].type) {
				msg += DriveTypeFlags[i].name;
				break;
			}
		}
		msg += '\n';
	}
	cout << msg.c_str();

	return 0;
}

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