By the fact that you mention GetDiskFreeSpace from the SDK, I am assuming that you are not using the CVI Function from the toolkit.
In this case, there is a new function in the SDK called GetDiskFreeSpaceEx. This avoids some of the maths involved with GetDiskFreeSpace function.
The new function uses value types of ULARGE_INTEGER.
If you use the CVI Version in the tool kit, this returns a structure of the following type:
typedef struct {
unsigned long int loBytes;
unsigned long int hiBytes;
} UInt64Type;
he "loBytes" member will contain the low-order 32-bits of the value, and the "hiBytes" member will contain the high-order 32-bits of the value. Use the function UInt64TypeCompareUInt to compare this value with a native 32-bit uns
igned long integer.
I've cut and paste from both the SDK Documentation and the FP Help from CVI to answer the above.
If you need more info, just shout.
Chris