Windows 7 Explorer Hanging Up Memory Like Crazy?

I'm running: Dell XPS 9100 Windows 7 Ultimate 64-bit SP1 16 GB RAM Quad-core Intel 920 @ 2.67 GHz C: drive = 2 TB RAID-0 internal drive set (2 disks) E: drive = 2 TB RAID-0 G-RAID external array attached w/ eSATA (2 disks) Today I had a serious problem with Windows Explorer. I was trying to access a 3.2 GB TIFF file on my external E: array (used for backup, Second Copy is my backup utility) and sorted the directory by Date Modified to find the file.Windows Explorer hung and spun for 45 minutes until I had to power-switch my computer off. Froze up everything. Consumed up to 14 GB of RAM with non-stop page faulting. I even got a black screen trying to start Task Manager to kill the process. The black screen hung, then threw an error msg saying it couldn't open the window and said either press ESC or power-switch the computer. Hitting ESC worked once, but the next time I tried it 10-15 min later I had to power-switch the machine.Windows upon restarting applied some patches during the boot sequence in a place I'd never seen it do that before (while the colorful logo on black background is coming up, before the normal 'Windows is configuring your computer' message on the blue background when it's updating).Lost all my configs - Start Menu, Desktop, Firefox bookmarks, IE favorites, Photoshop actions/recently-edited-files, etc. My files and programs seem ok, though, so far.In Resource Monitor the Windows Explorer window had taken almost 100% of memory, 12 GB of my 16 GB. Photoshop could not even close.It had spun like that on my internal C: drive. But defragging seemed to fix it. On my external drive defragging doesn't help much. Tonight, after defragging my E: external array, I again tried accessing the same directory to work with an updated copy of the same TIFF file. Again I sorted the directory in descending order to sort the file to the top. And I tried to delete another 3 GB file in the same directory. Windows Explorer kept the resources hanging for 20-30 min instead of 45+ minutes. But this time Resource Monitor said Explorer was taking up from 12.9 to 19 GB of memory (on a 16 GB machine).This time Explorer did allow Photoshop to close. But I had to kill the Photoshop.exe process after exiting Photoshop, and some minutes later the memory usage dropped from 19 GB to 98.7 MB.Has anyone seen anything like this? what's going on?My E: drive is external, used for backup, is 75% full and has 240,000 user files on it + whatever system files, Second Copy control files, etc.