Can I instal two different sims games (both sims 3) to my computer? My brother has chinese version of his game but I have english and even the language package doesn't give me asian languages only like german, swedish, spanish and so on. So I'd want to instal that other game version to my pc but still not un instal the english game version. Do you think any files would be overwritten if I would just instal the other sims into other harddrive since I have 3 of them?
Hopefully you get my point what I mean with this

Hmm...I'm thinking that as long you set the install area to either another drive, or to another folder in the same area, then it should be fine. It should also create it's own saves in the my documents area, in a different language then the original. However, i would think opening a save from the other one, would lead to some form of corruption.

Before anyone can answer that, we most likely need more information, like:
- do the both of you have your own user accounts on the machine?
- do you have 2 different sets of the game(s) and thus 2 registered accounts at EA where both of you are active and want to keep it that way?
- what region(s) are these game discs in? or are they digital downloads? The region with Chinese language would have English as well but the English language disc may not have Chinese.
- do you play the same game as you like the same CC or different set of CC and thus different save games?

I think that's all the pertinent questions for now (that I can think of), there might be more but they depends on your answers, really.

No, that is not possible. TS3 stores the language information in the registry under HKEY_LOCAL_MACHINE, which is universal for the computer. Installing TS3 twice on the same computer isn't possible anyway. If you're willing to change the registry (IIRC there're some tool for it) and reboot every time before one of you plays, you can both play in your favored language (ETA: if that language is supported by your version of the game of course).

No me and my brother have totally different computers, I just wanted to try his game on my computer. I guess I just uninstal my english version for now and play with chinese game version, tho I could change that into english later if I get option like that but then again all the money that went to english version games would be wasted Anyways thanks for all the replies!

When you say "try his game", do you mean that you want to play a game using his save files? If so, I'm not sure having a different language setting would make a lot of difference.

The only difference I'm aware of is the folder name. It's "The Sims 3" for the English and e.g. "Die Sims 3" for the German setting. It's probably sufficient to rename the folder if you change the language setting.

That's why AGS is !

But if you don't understand the game's folder structure, the languages and the registry entries, uninstall and reinstall though a hassle, is probably the safest route for the OP.
Provided proper backups is done and caution is observed, of course.