sketch_dec19a appears as default program

I am a real beginner and I've just bought an Arduino Uno and it is now up and running (I've tested the "Blink") under Windows XP. By mistake I've called the "sketch_dec19a" for compilation (causing errors) and now and can't get rid of it: it stays as a default program to be assembled. I'm just trying to restart working arduino with an empty map. Could you help me?

Delete the stored sketch_dec19a. Every time the IDE starts, it creates (or opens) a sketch with today's date in the name.

Or, just wait until tomorrow. The problem will go away.