Usually Word will only do this if the file format is not recognised as a native one. It will then offer to convert it to a suitable format which can be pre-selected on the menu presented. If it is a Word document and it is converted to shall we say .txt then all the formatting information for Word is also displayed and this can look like garbage but the actual text will probably be there later in the display. Same thing happens if you open a Word document in Wordpad.
I am just a little concerned that if it is an actual Word document this option to convert should not be presented at all which might be explained by the files being a little corrupted.