Emergency!!! - Fatal Error when confirming order.

My site has been operational and working fine for the last 5 months, and when I came into work this morning I had zero emails, which shocked me. We usually have 15~ orders on a weekend. Well I went to my customers -> Orders and orders were placed, but none of the confirmations were sent out or anything.

THIS IS THE ERROR THAT IS SHOWING UP.

Fatal error: Cannot redeclare class smtp in D:\inetpub\cheapstairparts\ZenCart\class.smtp.php on line 12

What the heck does that mean? I went to line 12, I don't see anything wrong.

HELP!

I deleted the file that was causing the error so I could test it out, and now it works fine.

No idea.

Well, considering that the class.smtp.php file that comes with Zen Cart v1.3.x is stored in the /includes/classes folder, I'm not surprised that having a copy of it elsewhere and doing something with the code to load it from a 2nd location would give you unexpected errors.
Deleting the file that doesn't belong seems appropriate.