The GetLogicalDrives function returns a bitmask representing the currently available disk drives.
DWORD GetLogicalDrives(VOID)
This function has no parameters.
If the function succeeds, the return value is a bitmask representing the currently available disk drives. Bit position 0 (the least-significant bit) is drive A, bit position 1 is drive B, bit position 2 is drive C, and so on.
If the function fails, the return value is zero. To get extended error information, call GetLastError.