Hey Simmers, I'm having a problem with my game. I don't know if it's because of my computer (it's very old), but when a Sim ages to old age, the game freezes. It happened with another Sim, but I changed their hair and they aged fine. But with this Sim, I changed their hair and clothes, and every time they're about to become old, my game crashes and I have to log out of my computer. What could it be? Does this Sim have to die before becoming old?

Probably they're just aging up into broken CC. You'll have to do a binary search. It's probably more useful to see where it crashes in CAS than just when aging up, though.

Sometimes the CC works fine in CAS but causes crashes on-lot under spesific circumstances (aging up, looking for job), so just checking in CAS might not give any results.

Sims usually grow up in either maxis clothes, default replacement clothes, or towniefied clothes (CC clothes that are set up to randomly spawn on townies). The latter two are the most likely culprits, since sims don't normally grow up in non-towniefied/non-default CC clothes.

Clothes that commonly cause these kinds of bugs are those made with the wrong base in SimPE/Bodyshop (tops made with a full-body base, for instance). They aren't easy to spot, unfortunately (you need to know what to look for in SimPE, occasionally also in Milkshape).

Thanks for replying. Many of my Sims have grown up wearing custom-made clothes, and it wasn't a default replacement... but this Sim, I've dressed him in all Maxis clothing, and nothing changes , except the skin color. How do I change it? I create them in random mode in Creator Sims... so he has to die before getting old?

You could find him in SimPE and change his skin to a Maxis code under DNA and under character file. It isn't difficult.
http://www.lothere.com/verso/page/16

Try giving the sim a maxis skintone.
If the sim currently has a custom skin, it's possible there's something wrong with the elder stage of that skin. Changing to a maxis skintone should go around this.

If sims grow up in custom clothes, the clothing items are most likely towniefied (and/or decustomized, meaning they blend with maxis, especially for added ages/genders).
I personallly don't use a lot of towniefied clothes, and my sims usually grow up in either maxis clothes or default replacements of these. They do get custom hairs, though (I think most custom hairs I've come across have been towniefied).

Honestly, I have tons of skin types downloaded. This one was really dark and I didn't know which one it was. This Sim was randomly selected and create , but you can mark this as solved and I'll explain how. There's a really interesting object I downloaded from this page called Skin Type Prototype or something like that. I applied Maxis's skin (I think it's only available in the game; it's a box, you click on it and select it). Well, I tried it and voila... the Sim became an old person! Yeah! I hope this helps someone. (Here's the CustomSkintoneSelectorPrototype from christianlove )