I am just a litte curious. I run Ad-aware at least every 2 weeks. Just now I found 36 critical objects. I have tried to get my sister to download the ad-aware program. She just isn't interested. So I am wondering just how much damage can happen if a person doesn't run an ad aware program.

Look at the number of HJT logs and the number of posts in the forums about computer problems resulting from such malware on their computer. Not running an adware programme will result, at best, at your being tracked all over the net, at worse, will slow your computer to a crawl or make surfing impossible.
Keep encouraging your sister to add this needed layer of security to her computer.
Cheers,
John