Thanks Neil, that's exactly the kind of insight I'm looking for!
Anyone have more thoughts to add?
I find Win98Lite ('98SE) with Firefox 1.5.12 to be a pretty good combination on a 300Mhz 600.
(Didn't know Firefox 3 would run under Win98 - must look into that ...).
Flashblock (1.5.6) is pretty much an essential extension with today's graphic-heavy websites, and Download ThemAll is mighty useful for it's resume feature. Irfanview for graphics and Total Commander for just about everything else, including file compression and FTP. I still use Outlook Express (out of laziness), but use MailWasher first to keep the junk away.