Returns the size, in bytes, of a specified drive.UnitSysutilsCategoryfile management routinesfunction DiskSize(Drive: Byte): Int64;DescriptionDiskSize returns the size in bytes of the specified drive, where 0 = Current, 1 = A, 2 = B, etc. DiskSize returns -1 if the drive number is invalid.
DirectoryExist('a:\')也可,没有专门的函数