Hi, seeing as everybody is talking about IE alternatives, of course mentioning Firefox, Moz and MyIE2/Maxthon, I would like to talk about my personal favourite, Crazy Browser.
It's kind of a freeware clone to NetCaptor, which is nice too but shareware; I like it because it's clean, stable and simple, as opposed to the mess that are Opera and the aforementioned browsers.
It has a lot of cool features (like saved tabgroups, undo close tabs) but not the ones I consider gimmicky like mouse gestures or a billion ways of handling each and every behaviour - I never thought about a feature I would like to have an extension for (argh @ Firefox) except for some cosmetic stuff.
It uses the IE engine so it could have security flaws, but you can disable ActiveX and stuff very easily and on a per-tab, inheritable basis. Then again, I have no AV, had no firewall before XP SP2 and never had any serious problem except the odd porn dialer in 98 times...
It's not been updated since the last ice age but it's very successful at catching the right popups and dead easy to configure. Try it and you might like it !
That's all :)
(PS : I try to switch to Firefox each and every version but am never satisfied with the look and feel, even after the whole install & configure N extensions rumba - and there's still small, unconsequential bugs everywhere which give it an amateurish feeling...)