I thought that since my computer is now a MacMini, and I no longer need to carry the computer around with me all the time, I could deactivate FileVault. Unfortunately, that won't work for now, as Mac OS X tells me that I need 4 terabytes of free disk space to deactivate it. I'll have to save up for a while before I can afford that.
I'm not the only one with this problem. Apparently, OS X makes a mistake in its calculation when it seems like there isn't enough disk space (even though my home directory only takes up 31 GB, but I have 44 GB free) when displaying the required additional disk space.