Private Declare Function GetDiskFreeSpace Lib "kernel32" Alias "GetDiskFreeSpaceA" (ByVal lpRootPathName As String, lpSectorsPerCluster As Long, lpBytesPerSector As Long, lpNumberOfFreeClusters As Long, lpTotalNumberOfClusters As Long) As Long

Private Sub Command1_Click()
 Dim free_Space As Long
 Dim checkDrive As String
 checkDrive = "C:"
 ChDrive checkDrive
 Dim numSectorsPerCluster As Long
 Dim numBytesPerSector As Long
 Dim numFreeClusters As Long
 Dim numTotalClusters As Long
 Dim success As Boolean
 success = GetDiskFreeSpace(checkDrive & "\", numSectorsPerCluster, numBytesPerSector, numFreeClusters, numTotalClusters)
 free_Space = numSectorsPerCluster * numBytesPerSector * numFreeClusters
 MsgBox "На диске " & checkDrive & " свободно " & Format(Str$(free_Space / 1024), "###,### ") & " Кб"
End Sub