"I created a new share to hold an archive, moved (not copied) most of the content from the WHS pictures directory to the archive, and then created a new folder pair (sync action) pointing from my pictures directory to the new share. Started a sync off and went to bed. Woke up to see synctoy happily deleting the pictures in my local pictures directory. Slowly deleting them, but... as I slept, it deleted about 27k files from my local pictures dir tree. So I recovered files from a WHS backup :-). (I restored the whole tree to empty space on the WHS machine, and then used synctoy to push files from there back to my workstation's pictures tree. That worked fine. The two copies windiff as equivalent now except for less than 200 expected changes.)"
It seems like when you moved the files, you left the old sync pair active, and SyncToy saw your moved files, as files that were deleted on the old folder. When seeing these, it assumed that it needed to delete the files at the other end. If you were to repeat this set of actions, make sure that you delete your old folder pair, (the one pointing at the old location where your images used to be).
You can try deleting the *.dat files on your synctoy folders (ie if your pair is f:\left f:\right, there will be some SyncToy*.dat) hidden files in these two directories. If you delete these files you will reset all the information for that store.
Maria del Mar Alvarez Rohena
Microsoft Sync Framework