Alternative Browsers
There are two types of alternative browsers. IE based alternatives and also completely different browser engines. IE based alternatives simply use Internet Explorer's main engine and add useful components. Usually popup blocking and somewhat better security and tabbed browsing. The advantage of them over plain Jane IE, is that they are better because of their added features. Their advantage over completely new browsers, is that sites which require Internet Explorer still work with them because they use the IE engine. The disadvantage is that they retain most of Internet Explorer's vulnerabilities.
I use both Netcaptor and SlimBrowser though MyIE2 and Avant are also very good. These four and many more are all based on Internet Explorer. All four provide both security and browsing advantages over plain old IE. They all have tabbed browsing, popup blocking and easy access to a menu to allow or disallow their security features.
Mozilla's new Firefox is also an excellent browser and safer than any of the IE based browsers above, but you may occasionally run into sites which do not display perfectly, or at all if the webmaster is incompetent enough. Firefox has tabbed browsing and popup blocking of course. You can have multiple browsers available and they should not interfere with each other. I have all of these and more on my computer without conflict.
Opera is another alternative, but seems more interested now in developing browsers for PDAs and cell phones. I feel it's development for Windows has slowed down. But, they just received a $12.75 million settlement from Microsoft for allegedly sending Opera users going to MSN off to a dysfunctional page.
What about Netscape or Mozilla? They are passé, but quite functional. I don't think they are as good as those above, and they are being replaced by Firefox. The latest version of Mozilla can be a good combo browser and email program though.