If so, restore the files from your Emergency Startup Disk or read the Help section on how to edit these files. You might want to load the two versions of each of the files into a text editor to see if you can figure out the line that is causing the problem. We'd recommend making a note of changes you make, just in case some other aspect your system's functionality is affected by incorrect use of this powerful tool. Hope you were backed up and had insurance. Unfortunately, if this has already happened, there's not much point in telling you to never plug in or unplug anything connected to your computer with the power turned on.
Computers are sensitive to static electricity, power surges and power failures, too.
Consider getting a power bar that promises protection against EMI, EMF, RFI and power surges. Some units even offer a guarantee against damage to your computer. Here's a collection of links to disaster recovery tools. The Seven Painful Truths of Windows Computing .