If your browser homepage keeps changing to something other that what you set it to, chances are you have picked up a spyware application known as a browser hijacker. This is not a virus and is usually easily removed. I would suggest getting a copy of AdAware and/or SpyBot Search and Destroy. These are both free and easy to find using a Google search. Either one will seek out and remove spyware applications in your computer. Spybot will also continue to monitor your computer's registry for unauthorized entries. If your settings keep changing after running either or both applications, you might try Hijack This. It does not remove spyware, but you can submit a logfile for analysis and suggestions. Also, if you do not have a virus protection application installed, do get one as soon as possible. AVG is free and is very effective. And install a firewall such as Sygate (also free) to prevent unauthorized traffic through your internet connection. The free Sygate firewall is no longer available. The Symantic "Smart Firewall" has replaced it, but is no longer free. Other free firewalls at this time are Comodo and I believe Zone Alarm still has a free version. There may be others that a Google search would bring up.