It happens to all.Its because of a download.What sims 2 versions do you have?It can also be because-
1-Download not compatible with version of sims 2 you have.
When was the last day it worked?Try to use clean installer
http://sims2pack.modthesims2.com/ and those that are red when searching downloads mean it is bad so delete one and try again then keep doing until game works