Open the file in MS Word.
Open Notepad. (Comes with windows, under accessories)
Copy and paste from MS Word to Notepad.
Then, copy from Notepad to the forum.
MS Word and the "helper" copy paste tool in Windows will "try to help" by pasting completely messed up code into the forum, which will make your post choke.
You will lose a lot of formatting, but if it's critical for the post, re-format it once you get it in the forum editor.