调用api函数getfreediskspace的返回值问题

[addishu]

你好！
我调用api函数getfreediskspace以求出硬盘的剩余空间，
但此函数在计算2G以上的硬盘时只显示2097MB左右
2G以下正确。请问为什么？怎样解决？

代码如下：

Dim SectorsPerCluster As Long
Dim BytesPerSector As Long
Dim NumOfFreeClusters As Long
Dim TotalNumberOfCluster As Long
Dim FreeDiskSpaces As Long
Dim bool As Boolean
bool = GetDiskFreeSpace(Drive1.Drive, SectorsPerCluster, _
BytesPerSector, NumOfFreeClusters, TotalNumberOfCluster)
If bool = False Then
MsgBox "call error", vbOKOnly
End If

'以BYTE为单位
FreeDiskSpaces = SectorsPerCluster * BytesPerSector * NumOfFreeClusters
'以MB为单位
FreeDiskSpaces = FreeDiskSpaces / 1024000

[Chen_Lin]

Private Declare Function GetDiskFreeSpaceEx Lib "kernel32" Alias _
"GetDiskFreeSpaceExA" (ByVal lpRootPathName As String, _
lpFreeBytesAvailableToCaller As Any, lpTotalNumberOfBytes _
As Any, lpTotalNumberOfFreeBytes As Any) As Long
-----------在程序中------------
dim a as long
dim b as long
dim c as long
dim d as long
d=GetDiskFreeSpaceEx(Drive1.Drive,a,b,c)
'得到以MB为单位
c=(c/1024)/1024