Afy,
For external ballistics, I like Point Blank. It's cheap (Free) and works quite well. The only internal ballistics program that I'm aware of is Quick Load. It costs several hundred dollars, and because of that I don't personally own it. I usually contact a friend who has it and ask him to run my data thru the program. It works really well, and gives you pressure readings for ever increasing charge weights and changes in OAL.
Don