Actually come to think of it...if your still using Windows 98 or ME your computer is probably too slow for Dreamcast emulation. I'm sure there's the odd person that installed 98se on a modern PC but the majority of PC's running Windows 98 or ME are probably 1ghz or less. Windows 98 is much faster on a slower computer with not much RAM but I would much rather run at least Windows 2000 on any computer I had. Windows 2000 is much more stable, doesn't require to be reinstalled as much, supports more of the latest software, way easier/more configurable networking, and I would say much more secure but that's not so much the case anymore with all the exploits people are finding.
Some people may argue that Windows 98 is plenty stable and doesn't need to be reinstalled often but that just means you don't push your computer hard, uninstall/reinstall software often, download a lot of stuff, and add new hardware semi frequently.