MacBook (2007 version) running 10.5.6

I created a graphic in Adobe Photoshop, saved it as precinct.psd in a folder on my desktop. I rebooted the next day and on my desktop there was the file called precinct.log. A month later, the original file is gone, and every day I delete the precinct.log from my desktop and every day that same **** file reapears. Does anyone know what the heck is going on? I am obsessive on a clean desktop and this file really bugs me.