Writer files associated with Paint

[A. G. Moore]

a few days ago I noticed that all my text documents were being saved as paint documents. While I can open these files by indicating that I want the document opened with open office, this requires an extra step. Also, and more importantly, the fact that the document is in paint seems to be confusing to people with whom I share the material (send as an attachment). What did I do wrong and how to I fix this?
Thanks A. G.

Edited title to make it more informative - floris v, moderator