You might ask "What's microdock?" It's my personal name for what you get when you're trying to drag a large selection of something (images, for example) and drop it onto a folder in the dock (say a new destination folder) ... and miss the target. When this happens, the 1,254 images you were trying to place in "My Pictures" are instead added to your dock ... and you get the microdock (a 10K image file, but it's 1600 pixels wide).
So how do you recover, as the only obvious way to get the stuff out of the dock is one item at a time? There's a quick two-step solution. First, delete com.apple.dock.plist from your ~/Library/Preferences folder. Second, use ProcessViewer (or the Terminal) to quit the dock. When it restarts, you'll find a new dock with the default OS X icon set installed.
If you had a highly customized set of things in your dock that you'd rather not have lost, you're out of luck at this point (short of hand-editing the dock.plist file). In the future, though, create a backup of the dock.plist file while the dock is "good", and then just replace the "bad" dock.plist file with your good backup and restart the dock -- you'll have your pre-incident dock back complete with customization.
The publication of this hint is in no way an admittance that I may have actually done something like this, of course ;-).
Mac OS X Hints
http://hints.macworld.com/article.php?story=20020410223951370