>You've to specify in DECLARE that those parameter're passed by reference, properly initialize them and pass by reference to the function.

DECLARE LONG GetDiskFreeSpace IN kernel32 ;
>	STRING, LONG @, LONG @, LONG @, LONG @
>LOCAL ret, strDrive, lngSectors, lngBytes, lngFreec, lngTotalc
>STORE 0 TO lngSectors, lngBytes, lngFreec, lngTotalc
>ret = GetDiskFreeSpace(strDrive, @lngSectors, @lngBytes, @lngFreec, @lngTotalc)
>? ret, lngSectors, lngBytes, lngFreec, lngTotalc
>
>

The function GetDiskFreeSpace has a bug. See faq #7847 for to how get correct info.

Actually, it isn't a bug, it was a limitation based on the technology at the time it was written. Since any signed integer greater than 2gb is a negative number, the function caps the maximum result at that amount. This is why GetDiskFreeSpaceEx() uses a datatype known as ULARGE_INTEGER (an unsigned 64 bit integer. In reality, this is actually a structure made up of two DWORDs.