Just enter their name into the search feature on any given board in the place for the post's author, set the date as far back as you like and hit enter.

You will have to do it board by board.

You won't find any posts where they use an alias of course.

That's what reviews are for: reading.  If nobody read the reviews, there would be no point in writing them.

Like fisher said, check the search feature.

FYI if you are going to use this to stalk or harass someone, the admins WILL BAN YOU from the forums, even if you use an ALIAS