Is it possible someone using your computer , has copied some text from word or note pad and accidently saved it to the desktop ? this by far would be the simplist cause .
Your search is part right , these files can be used in the manafactur/running of viruses/trojans , with the correct code and a little knowledge , some bits from Windows it can be done , i`m not saying anymore than that as it would be irresponsible .
Have you checked the properties of the file to when it was created ?
You can copy and paste it into a new word/notepad document , to see what it is , i would only advocate doing that after trying everything else.