I use all these,all free.
http://www.safer-networking.org/en/index.html
http://www.lavasoftusa.com/software/adaware/
http://free.grisoft.com/freeweb.php/doc/2/lng/us/tpl/v5
And this should stop hijackers from taking over your start page.
http://www.javacoolsoftware.com/spywareblaster.html
This is Steve Gibsons site who shows you why ports 137,138 and 139 don't need to be open and provides a way to close them.Most important thing you can do,I believe.Just watch all the pings to those ports on your Zone Alarm software,all aiming for those open ports. It's Microsoft file sharing ports but most home users just don't need them. Has a couple of buttons ,NoShare and LetShare to let you turn it off or on.
https://grc.com/x/ne.dll?bh0bkyd2
You might have to do this first to get rid of the bot. Hijackthis.
http://www.spywareinfo.com/~merijn/downloads.html
And do it in safemode too.The whole process means a lot of shutting down and restarting but it is agony to redo your start page time and time again.