Iffn' you're going to be using Win98, you won't be able to do this from within the OS itself. You'll have to get one of those fancy-schmancy RAID controllers.

[link|http://www.newegg.com/app/ViewProductDesc.asp?description=16-115-002&depa=1|http://www.newegg.co...16-115-002&depa=1]

Try this one, reviews seem pretty good. The way it works is you buy 4 or 8 hard drives, attach all to the card. When you boot the machine, it gives you an additional option during the POST sequence to enter the controller's BIOS. From there, you have a whole host of options to follow through, that reconfigure those hard drives to be one "big" drive. As far as Windows 98 goes, it thinks you just have one giant hard drive, with parity bits. If a drive fails, you replace the drive, and the RAID system restores the data from the parity bits on to that drive.

If you're excessively paranoid, do a 4-way mirror. :)