Yes, that's on drive C:, but how much diskspace occupy the recycle bins on drive D:, E:, ..... ? If the user wants to defrag e.g. drive C: only then DF simply wants to empty all recycle bins on all other drives as well.
You say you never use the recycle bin but I am not so sure of that. I know - at least - one program that uses the recycle bin: Outlook Express (OE). When OE compresses its folders then it moves the old uncompressed folders to the Recycle bin. So, perhaps Outlook and other programs use this ""trick"" as well.
B.T.W. Do you already use Ccleaner ? (from the Piriform folks as well).
I can understand that you're very careful to keep your drives as clean as possible, especially when I see who your employer is. And that's why Ccleaner is such a wonderful cleaneing program. It's highly customizeable.
Well, then you'll have to dig a little deeper. Use a program like ExplorerXP, Treesize or JDiskreport to see in which folder that 2 GB is hiding. Perhaps that 2 GB is hiding in (the Recycle bin in) that folder Sandbox ? It appears to be only 2 months old.