You must design your site with a demographic in mind. Then, knowing your demographic you can decide whether or not they're likely to meet your minimum requirements. Windows XP for instance wont go below 800x600. While I wouldnt' design a site which didn't work at 800x600, I also don't make allowances for people running at 640x480, especially if I'm making a comercial site. The truth is that people running a system without Flash 4 installed, on 640x480 aren't the demographic for most commercial sites; in terms of avilable capital to spend.
Most large institutions (take my University for example) run at least
IE4 which comes with Flash 4. Increasingly, large sites like Microsoft, CNet and others which have massive audiences are using Flash and not allowing for those without. It's a web trend. Tell your boss to get with it
Please don't email or PM
me Flash questions, that's what the Forums are for!
Please don't rely on me reading my PMs either. Email me about important stuff.