When you use Open With do you select the Choose Default Program option? If you tick the appropriate box within that then Windows remembers which program to always use with a particular file extension (i.e. the part of a filename that indicates what type of file it is).
What program (and version) are you using for your emails?
If it's Thunderbird then go to Tools > Options > Attachments to choose which program opens what type of file. If not then I don't have it to have a look.
"When I choose open with i am choosing micro soft word"
are you selecting word from the pop up menu, or have you tried selecting "choose default program" (or something like that, it's at the bottom of the open with menu) and then choose word and make sure the always open with box is ticked.