Here's the registry key to change:
HK_LOCAL_MACHINE/ENUM/ESDI/GENERIC_IDE_DISK_TYPE47
Go the the folder below this. Make sure the "CurrentDriveLetterAssignment" matches the drive you want to rename, then modify the "DeviceDesc" key to read whatever you want. Whatever you type in here will show up in Device Manager as the description of the hard drive.
I read this on another post a long time ago: Windows 98 may label the hard drive correctly if you are using busmaster drivers provided by the motherboard chipset manufacturer. You get the "generic" label if you are using Windows built-in busmaster drivers.
In my case, the older VIA busmastering drivers used to correctly identify the drive, but the newer ones don't.