Well my friend was making a map and he wanted probes to automatically mine in the beginning, so we were looking through AI scripts and we weren't sure if there was one with automatic mining. Is there one with automatic mining?

And I also heard that there was a program allowing you to make your own AI scripts. Is this true?

Most of the AI scripts will mine, but some give different results. Such as, in a map of mine, the computer insisted on using only one peon to mine and sent the rest to the enemy base. Not exactly smart.

Changing/creating AI Scripts is only possible via modding.

If you want custom AI scripts, you will need to create a mod with your custom AI. Everyone will have to load the mod before starting StarCraft.

dam, oh well that sucks. thanks.

Refer to the AI script I mentioned in this topic.
http://www.staredit.net/topic/7971/
It's a default one that everyone has.