Weird System Info!

[arpan_de]

I am using the following code to get the system information of the user's machine. A ImageCombo lists all the hard drives. Since I want only the hard drives, I am using the ImageCombo & not a DriveListBox (NOTE: This isn't my code):

Private Declare Function ShellExecute Lib "shell32.dll" Alias..........
Private Declare Function GetVersionEx Lib "kernel32.dll" Alias..........
Private Declare Function GetDiskFreeSpaceEx Lib "kernel32.dll" Alias..........
Private Declare Sub CopyMemory Lib "kernel32.dll" Alias..........
Private Type ULARGE_INTEGER
    LowPart As Long
    HighPart As Long
End Type
Private Type OSVERSIONINFO
    dwOSVersionInfoSize As Long
    dwMajorVersion As Long
    dwMinorVersion As Long
    dwBuildNumber As Long
    dwPlatformId As Long
    szCSDVersion As String * 128
End Type
 
Dim OsInfo As OSVERSIONINFO
Dim tmp As String
Dim FreeUser As ULARGE_INTEGER
Dim Total As ULARGE_INTEGER
Dim FreeSys As ULARGE_INTEGER
Dim Temp As Currency
Dim fTemp As Currency
Private Declare Function GetLogicalDriveStrings Lib "kernel32" Alias.....
Private Declare Function GetDriveType Lib "kernel32" Alias.....
Private Function [b]GetDriveTypeFromLetter(strDriveLetter As String) As String[/b]
    Dim strDrive As String
    If Right(strDriveLetter, 1) <> "\" Then
        strDrive = strDriveLetter & "\"
    Else
        strDrive = strDriveLetter
    End If
    
    Select Case GetDriveType(strDrive)
        Case 2
            GetDriveTypeFromLetter = "Removable"
        Case 3
            GetDriveTypeFromLetter = "Fixed Hard Drive"
        Case Is = 4
            GetDriveTypeFromLetter = "Remote"
        Case Is = 5
            GetDriveTypeFromLetter = "CD-ROM"
        Case Is = 6
            GetDriveTypeFromLetter = "Ram disk"
        Case Else
            GetDriveTypeFromLetter = "Unrecognized"
    End Select
End Function
Private Sub [b]Form_Load()[/b]
    Dim strSave As String, i As Long, ret&
    Me.AutoRedraw = True
    strSave = String(255, Chr$(0))
    ret& = GetLogicalDriveStrings(255, strSave)
    For i = 1 To 100
        If Left$(strSave, InStr(1, strSave, Chr$(0))) = Chr$(0) Then Exit For
        If GetDriveTypeFromLetter(Left$(strSave, InStr(1, strSave, Chr$(0)) - 1)) = "Fixed Hard Drive" Then
            imgCboDrives.ComboItems.Add , , Left$(strSave, InStr(1, strSave, Chr$(0)) - 1), 1
        End If
        strSave = Right$(strSave, Len(strSave) - InStr(1, strSave, Chr$(0)))
    Next i
    Call GetDrive("C:\")
    imgCboDrives.ComboItems(1).Selected = True
End Sub
Function [b]GetDrive(DriveName)[/b]
    On Error Resume Next
    Dim retVal
    lblSysInfo.Height = 985
    OsInfo.dwOSVersionInfoSize = Len(OsInfo)
    retVal = GetVersionEx(OsInfo)
    
    Select Case OsInfo.dwPlatformId
        Case 0
            tmp = "Windows 3.x"
        Case 1
            tmp = "Windows 95/98"
        Case 2
            tmp = "Windows 2000"
    End Select
    lblSysInfo.Caption = "Drive: " & Left(DriveName, 2) & vbNewLine
    lblSysInfo.Caption = lblSysInfo.Caption & "Version: " & OsInfo.dwMajorVersion & "." & OsInfo.dwMinorVersion & vbNewLine
    lblSysInfo.Caption = lblSysInfo.Caption & "Platform: " & tmp & vbNewLine
  
    GetDiskFreeSpaceEx Left(DriveName, 2), FreeUser, Total, FreeSys
    CopyMemory Temp, Total, 8
    CopyMemory fTemp, FreeUser, 8
    lblSysInfo.Caption = lblSysInfo.Caption & "Total Space: " & Format$(CCur(Temp) * 10000, "#######,##") & " bytes" & vbNewLine
    lblSysInfo.Caption = lblSysInfo.Caption & "Free Space: " & Format$(CCur(fTemp) * 10000, "#######,##") & " bytes" & vbNewLine
    lblSysInfo.Caption = lblSysInfo.Caption & "Used Space: " & Format$(CCur(Temp) - CCur(fTemp) * 10000, "#######,##") & " bytes" & vbNewLine
End Function
Private Sub [b]imgCboDrives_Click()[/b]
    Call GetDrive(imgCboDrives.Text)
End Sub

The above correctly computes the total space & the free space of the drives. Now it's pretty obvious that since I have the total space & the free space, the used space will be (Total Space - Free Space) but strangely, that gives the wrong result & that too a negative value! For e.g. in my machine, the total space of C:\ computed comes to 10,000,343,040 bytes & the free space comes to 934,223,872 bytes; so the used space should be 9,066,119,168 bytes but VB computes it to -933,223,838 bytes! I have checked the other drives as well - the outcome is always a wrong negative value.

Why this huge discrepancy & wrong result in the used space?