Is it actually always on or just most of the time? If it’s ALWAYS on the HDD LED might be on backwards. Do you have any disk defrag utilities on your system? Some of these programs run constantly in the background defraging your disk. They generally don’t eat up a lot of cpu time or take disk access from other programs but they do access the disk constantly. Does the light come on and stay on at POST or after you’re in Win98? Try booting from a floppy into DOS and see if the light’s on. If it is, then it's probably the LED or the MB. If it's not then it something that's loading w/ Win98.