How do I find out the drive letters in use on a given system?

This one's easy. You need to use the cunningly-named GetLogicalDriveStrings API.

int iStrsLen;
char smzDrives [(3+1)*26+1];
char szDrive [3+1];
int i;

iStrsLen = GetLogicalDriveStrings (sizeof(smzDrives), smzDrives);

if (iStrsLen == 0)
{
// Handle error
}
else
{
if (iStrsLen > sizeof(smzDrives))
{
// Buffer not big enough... eh? - I provided space for all 26 !?!
}
else
{
// Parse the returned multi-string array.

i = 0;
while (smzDrives[i])
{
strcpy (szDrive, &(smzDrives[i]));

// szDrive now contains the root folder of this drive. I
// put this in a listbox here:

m_ctrlListbox.AddString (szDrive);
while (smzDrives[i]) i++;
i++;
}
}
}

Author : Bob Moore