Not sure if windows supports sparse files but I did the same task in unix by making a *SPARSE* lock file that was the same size as the file I was copying and used that in my size calculations. 

        sysopen( $fh, $lock_filename, O_RDWR | O_CREAT );
        seek($fh, $filesize,0);
        truncate($fh,$filesize);

[download]

Then a stat call gives us the sparse size while the filesystem hasn't grown at all. To get a rough idea of free space you can tally the free space the FS reports minus the sum of the size of all your sparse lock files.

Update: Code typos fixed

In reply to Re: Need Advice on Folder/Drive locking by bot403
in thread Need Advice on Folder/Drive locking by kuldeepchowhan

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