Help I lost all the lots in my neighborhood

I have windows vista (I know it's not really compatible but its been working fine for about five months.
2.8 GH Processor 1526 MB RAM
Sims2 Base Game only
I was playing strangetown the last time I played and when I restarted the game everything in the neighborhood was gone...everything... maxis stuff included. I have some custom content but I don't think I installed anything before I played it last. I did leave the program running all night the last time I played but saved and shut down normally the next day. I checked my neighborhood folder and the lots folder is empty but all my characters are still there. Is there anyway I can save my sims and get my families back??
When I open the neighborhood in SimPE everything looks fine except there are no lots. Please someone help if you can I spent months building families and relationships.