To find them - expand the Find & Replace
dialog and check "Use wildcards"; then, in the "Find what" box enter
"[A-Z][A-Z]" (without the quotes). I don't think there's an easy way to replace
them through the UI, but it wouldn't be hard to automate with a bit of VBA, like
this:
For n = 1 To
26
ActiveDocument.Range.Find.Execute
_
FindText:="([A-Z])" & ChrW(n + Asc("A") - 1),
_
ReplaceWith:="\1" & ChrW(n + Asc("a") - 1),
_
Replace:=wdReplaceAll,
_
MatchWildcards:=True
Next
For future reference - if you check the
AutoCorrect box (Office button > Word options > Proofing tab >
AutoCorrect Options) for "Two initial capitals", Word will automatically correct
them as you type.