See if you can get Microsoft Office Picture Manager..
Open up the thumbnail view, then just select one of each of the dupes, click file>Export and copy them off into their own folder.
5-600 pics sound like a lot, but it really won't take you that long. No more than an hour. I go through a thousand football pics in an hour to select out the good ones.
IF you can't get that office picture manager, try the large icons view in windows explorer, again, select one of each dupe ( ctrl left-mouse ) then drag to a different folder. I would suggest copying off the ones you selected on each 10 or so.. 'cause it really sucks when you have 50 selected, then accidentally hit the shift or double click. Trust me.