XML files....

[wild orchids]

Hi all,
Sorry if this is in the wrong forum, but I'm just a little loss.
I was trying to make changes to my skin.xml for rltoday, and as far as I remember, whenever I open the .xml file to make any changes, it opens using notepad and I can just make my changes there. However, as of yesterday, whenever I try to open that particular file, it opened using IE, and in order to change it, I'd have to rename it to skin.txt & go from there.
It's not a big deal, but I'm just curious as to why it happened, and whether or not there's something I can do to fix it so that I wouldn't have to rename my file.
Thanks.