To change file type association for .txt files to wordpad instead of notepad, follow below steps:
Open Windows Explorer, go to Files->Tools Folder Option then click on the Files tab.
Look for your file type ".txt"
Click on the Advanced button, and then look at the list of Actions. click on Open and then on the Edit button.
In the small dialog, look for the line that says "Application used to perform Action:"
Make sure the %1 in there is surrounded by quotes. if there is no %1 then added in your self, so the action looks like
Ok i hope this one helps a lot for those who need.