Cant change default home page! Or Homepage Hijacking.
Here's a post about...
Parasite removal programs.
http://reviews.cnet.com/5208-6132-0.html?forumID=32&threadID=1313&start=0 notes the five scanning tools and removal tools that are fairly safe. If one does encounter an issue, its always been damage done by the MALWARE. The most common issue being Layered Service Provider replacement which you can use LSPFIX (Hint: use http://www.google.com to find).
The thread has follow on discussions about new links if you don't want to use Google to find an item.
PS. All the tools are free.
i have yahoo as my homepage/serach engine. every time i restart my computer, it has changed to some weird search engine. i change it in internet options, but it won't stay on yahoo.