Still can't imagine how you managed it haha. Right no sweat on this and take it steady, you cannot do any harm as long as you don't go off piste.
1. In the search box bottom left in the task bar, type Default Programs
2. Look for "Choose a default app for each type of program" grey box.
(This opens up a settings dialogue box and can take a little while to load depending on what is in there) so wait!
3. When a list appears look at the far left info( in that pesky box) and scroll down the big long list to .XML that has XML Document written underneath it. Now on the right of that you should see a box that has unbelievably the Internet Explorer icon. If it hasn't, maybe it has something else or a plus sign, click whatever icon is there and from the list choose the Internet Explorer icon. Tick an always use this app box if it is there. (I have not gone the full distance cos I don't want to screw my setting up) If you do not want to go through this I suspect that the next time you run an upgrade or patch from Microsoft then it will automatically sort itself out.