In Word, click on Tools | Options | Edit | check the "Typing
replaces selection" box | OK.

chickclimb wrote:

For some reason, this started happening yesterday.

When I go to replace a word, I highlight it, then start typing. Previously,
the old word would disappear, and the new word would replace it. Now the old
word stays, and the new word appears in front of the old word.

I'm sure there is a function to change it back.

Please help!