Mac Mini has slowed to an unbearable crawl! I've read a lot of other questions about speed, but my question does not seem to be answered anywhere.  My Mac Mini is running so slow that I cannot see what I am typing. It takes up to 15 seconds to see the text I just wrote. Any process on the computer runs so slow that I see the spinning beachball all the time. 

I've looked in the Console and Activity Monitor, and cannot figure out what is wrong. No single process is taking up more than about 10% of the processor and memory is not maxed out.

I should note this is not a very old computer. It is not the most current, but it is fully capable of running Mountain Lion and has a decent amount of RAM.  Please help, I'm about to jump outta my window!
Before I even saw your DropBox Link, I was about to say it's DropBox Syncing the Files ON your Computer (MacMini) with your Online DropBox Account. This happened to me, as well. I emailed DropBox and they said it is normal during File-Sync. I went into DropBox Settings in the MenuBar and UnChecked All the Folders, so that the Files don't have to be on my Local Computer AFTER they have been Uploaded to DropBox.com (So, they were only needed locally to initially upload to DB without uploading via the website/browser. This is helpful if you have many Folders and Files inside other Folders.) Since the Upload was successful, I also turned-off DropBox Opening at Computer Startup.