This isn't a HeadOn commercial, you don't need to repeat the same message over and over again. If it crashes on the loading after you successfully installed a car, it's most likely that you're using version 2.0 of San Andreas. Practically all of the San Andreas SKUs sold in stores today are version 2.0, indicated by the words "Second Edition" on the box.
Try using a downgrader first, and then install a car like what you tried to do.
Some say that a No-DVD patch can also be used for downgrading, especially for users who got their SA off Steam, but since the DVD bypassed EXEs can be used abusively (i.e. for piracy), we're don't really encourage using such a patch. You may google one if you like, but do it AT YOUR OWN RISK.