So my computer got messed up last week?

and we took it to ciruit citys Firedog. we got it back now. we lost everything, and by that i mean pictures and reports and all that. now its like new. adn internet is slow, as well as the computer. what can i do to make it faster, adn protect ti . i got AVG and Norton anitvirus. aslo, i want yahoo to be my homepage. i am using right now internt explorer, and i dont want all that stuff on the top, like google search and all i just want yahoo to appeear without google serach and all that. so hlp plz.