How to eject a USB3 drive when Windows has handles open?

Argh! This is so annoying. You would've thought that Windows would have gotten this right by now.

I've got a 2TB USB3 external (obviously) HD that I want to eject, since when I mounted it last time it complained about an unclean dismount (don't remember what the exact message was).

So I closed all the application that I was using to access that drive and then proceeded to eject the drive, at which point I get a:

Problem Ejecting USB Mass Storage Device                                   |_X_|

   ^
  /|\  This device is currently in use.  Close any programs or windows that
 /_'_\ might be using the device, and then try again.

                                                                     [   OK   ]

dialogue.

I used Process Explorer and I get a bunch of processes which I closed or killed (like, wtf is Windows Media Player Network Sharing Service? I didn't start that. PresentationFontCache.exe? NO. avgidsagent.exe? Eff off!)

Now I just have System, services, and lsass processes running which are windows processes, so should be able to handle this problem, but it doesn't! Grrrr.

Any idea what to do with this crap? I can't just shut these down. And I'm tired of potentially playing Russian Roulette with my data. Why hasn't this been fixed in windows by now? This is so annoying!!

Running Windows 7 HP SP1

Here are the processes: