You can go backwards with no problem. Uninstall all of Netscape and then check out a program called "regcleaner" (a freeware application to help you clean up your registry).

Problem with 4.x of Netscape is that it just doesn't support CSS very well (half of CSS-level 1 support) and supports its own version of DHTML (using layers). One of the things that 6.2 gives you is the full CSS/DOM support.

Webmasters then have to make a choice. Do they not make use of current technology, build multiple pages to support older browsers, ignore it and let you suffer, or not let you into their site. Its OK now, but one more iteration of technology and you will start to see people shifting away from the 4.x browsers.

If your not IE fans (and I think IE6 is a fantastic browser), check out Opera 6.0