Hello Ashley,
I think before this question can be answered in the most complete and helpful fashion possible, we need a little more information (not ordered in terms of importance):
What AntiVirus software did you install?
What viruses (if any) did it find? Was it able to quarantine/clean everything?
When you say that your internet speed is very slow, have you tested it to see just how slow? Hard numbers are nice....
When you say that Yahoo and Google aren't working, what exactly do you mean? Are they taking a long time to load? Are they coming up as "Not Found"?
What is your system information? OS? etc.
I'm sure we can get you back to tip-top speed, so let us know!
