Sometimes I run into a problem when a save of a city tile is corrupted - the game either crashses shortly after the splash screen/image (when the region is being loaded), or when trying to load a city tile (when the tile is being loaded). There is no easy way to restore a corrupted save, since the problem lies with the old file being overwritten. Things would be a lot easier if the file is deleted, where you could restore from the recycle bin, but this is not the case of accidental/intentional overwriting.
I have discovered a nifty feature that utilizes the restore points that are created in Windows (not sure if it is available for XP, but the last time I checked, it's available for Vista and Windows 7). However, your city tile can only be restored to the last time your computer creates an automated restoration point, so you have to mentally prepared to lose some changes (and major ones if you happen to play heavily recently). Nonetheless, it is better that starting all over from scratch.
You simply have to right click on the file and select "Restore previous versions".
(https://www.sc4devotion.com/forums/proxy.php?request=http%3A%2F%2Fimg707.imageshack.us%2Fimg707%2F787%2Frestore01.png&hash=b3582bd39529d2d1303cb2a876475e088d7f1929)
The computer will search for previous versions, and if any, will display them in the dialogue box. You can revert to the previous version by replacing it rightaway, or copy the previous version to a location elsewhere in your computer.
(https://www.sc4devotion.com/forums/proxy.php?request=http%3A%2F%2Fimg6.imageshack.us%2Fimg6%2F8104%2Frestore02.png&hash=02430b6e95919cd1a6dab36b45d526df779aacaf)
I hope this helps!