ive used mozilla for years! ie and outlook express is just too full of security holes.
now i use firefox and thunderbird for mail. i sleep a lot better!
if you dont have a firewall program, i recommend getting one.. ive used agnitum outpost firewall for a long long time. it has some good plugins like ad-blocking in it too
while im recommending things,
http://free.grisoft.com/ the best free anti virus