Every time i play a final fantasy game on the ds emulator,it crashes.
It usually causes my whole computer to freeze up and need to be restarted.

I stopped playing ds emulator games,because its bad for my computer to be restarting so much.

So:anyone able to help me with this problem?

I'm sorry, but I've never used a DS emulator before - my guess is probably either the emulator itself it buggy and unstable, or your computer probably isn't powerful enough to run the game. There is also a possibility that FFIII/IV DS probably don't run well on that emulator either compared to other DS games, but as I said, I have no experience with DS emulation so I have no idea what the problem could be (my old DS phatt still works well so I just play FFIII and IV on that instead ;)).

All I can suggest is check the help file that might have come with the emulator and see if there is any known bugs with FF titles on it - usually emulator authors will try to fix such bugs and try to get games running on them if they don't, but it might be a while before that happens.

EDIT: okay, I've recently tried a DS emulator on my system (DeSmuME) and although I haven't tried either FFIII or IV DS on it yet (I've only played Castlevania Portrait of Ruin with it so far, which runs at half speed and the sound/music is glitchy), I think it might just be indeed a case of the emulator you're using might just not be compatible with those games yet. Try using another emulator and see if that helps.

Which emulator are you using?