I'm typing this in Windows 98 with a 200MHz Pentium right now. To get things all up to date, look at Wikipedia and mdgx.com, plenty of information to get you going. Thing that sucks is that Microsoft's installer for Internet Explorer 6 Service Pack 1 does not work anymore, so IE6 is the highest you can go. There are some other updates I could install that require service pack 1 to be installed... but oh well I guess.
Security is an issue if you are using this computer for all of your browsing, but I'm sure you have something more modern for all of your sensitive information. Even if you don't, you could always run Linux and use w3m for browsing.
Premio 212B motherboard (MSI MS-6112)
Intel PentiumII 333MHz Slot 1 66MHz bus
384MB ECC 66MHz
SIIG ATA133 controller --> Seagate Barracuda 80GB
SIIG Gigabit Ethernet (RTL8169) / USB 2.0 / IEEE1394 controller
ESS 1869 soundcard on board wavetable synth