How do I stop The Sims 2 from crashing when I go on to a particular family?

Try removing some downloaded content, especially hacks. Delete all .txt files in the Logs subfolder in Username\Documents\EA Games\Sims 2, and delete everything in the \Sims 2 subfolder with .cache on the end of it.

If you have a modified Userstartup.cheat file in the \config subfoler, move it to the desktop.

Then, startup up the game. It will create new logs and settings, and, if it works fine, move custom content back into the game one at a time, until you pinpoint the problem-causing download.

Hope I've been ov help,

--Qahne Yssi