Can anyone tell me how to reload the old neighborhoods so they will be playable again?
You could try this (that's what I usually do when I want to reload old 'hoods and have never had any problems):
- Rename the My Documents/EA Games directory to "EA Games_old" or whatever
- Fire up the game to generate a new, clean EA Games directory. Quit game.
- Transfer old "Downloads", "Saved Sims" etc. folders you want to keep to the new EA Games directory
- Replace new neighborhood folder "N001" with your backed up "N001" folder (for example).
- Delete "NeighborhoodManager.package" (in My Documents/EA Games/The Sims 2/Neighborhoods)
- Profit
This will only work, of course, if your old 'hoods were NOT being played in a more recent EP "environment" than the new ones (e.g. old 'hoods up to AL and new ones only up to BV).