What's eating up space?

I've added a lot of content to my Xoom, but it surprised me when I plugged it into my computer and saw, "8 gb free" - I didn't think I'd used that much.

Here's what I'm seeing: through Windows, at the top level I see 8.08gb free of 28.7". By my math that means I've used 20.6gb.

But, if I ctrl-A -> Right Click -> Properties (again through Windows) I see a size of a bit more than 17gb.

So, Windows is telling me I've used 20gb, but it can only 'see' 17gbs being used. Any suggestions on how I can figure out what's using the 3gb? I'd use the program "disktective" which is usually perfect for this sort of thing, but it doesn't seem to see my Xoom. Normally I wouldn't care about a measly 3gb, but if I've only got 28 to play with. . .

 

Thanks - I wasn't aware of that tool. But, it just tells me that X amount is used by media and X amount is used by applications. I see now the mysterious 3gb must be classed as 'media', thanks for the clue.