Chuck,
If you need to change the extension ( ie to *.txt) you need to do two things.
Windows defaults to hide those extensions from you, making it VERY annoying to try to change the.
so step one is, get windows to show you the file extensions (the part after the dot)
here are instructions I found after a quick Google.
http://www.fileinfo.net/help/windows-show-extensions.htmlOnce you have done that all the files will get the dot and the rest showing up.
Then Copy your file so you have a backup, right click on the backup, from the menu that pops up, select rename.
The cursor will show up on the name and you can edit it to be what you want.
When you are done click away or hit enter.
If you change the extension it'll warn you it might make it unusable, hit ok,
and you should be done. Don't remove the dot, and if you keep the part after the
dot to 3 characters you'll be happier.
Hope that helps.
Eric-