Help MY MINECRAFT KEEPS CRASHING?

I downloaded the Mo creatures mod for my minecraft and watched a video on how to make it work. AND NOW EVERY TIME I TRY TO PLAY ******* MINECRAFT IT KEEPS CRASHING. How can i fix this should I reinstall minecraft?!

How to install my Minecraft mods?

I put the Modloader folder into the minecraft bin folder. Then put my mods into the mods folder found under appdata, I then tried to get on Minecraft and it crashed. Any help?

Why does my minecraft keep crashing?

I have this problem with minecraft, when ever i play for 5-10 mins. A black box pops up with white writing in it and its for java, if i exit the box minecraft exits, but if i leave the box there after about 30 seconds minecraft will close. I have tried deleting my mods, restarting my.minecraft folder and nothing works. Does anyone know how I can fix this?