It probably is set for ATA100 mode, and you need to jumper it to ATA66 or some lower mode. Most 80 Gig drives are designed for faster systems, and old BIOSes won't detect them due to the disk geometry being over the BIOS max size. You'd have to upgrade the BIOS to support it, if the BIOS upgrade does not support 80 gig drives, you a SOL for that system unless you buy an ATA100 PCI controller and use a boot-sector driver that comes with the 80 gig drive.
My advice is to take the drive back where you got it from. Then find a smaller drive on the Internet somewhere. 20 gigs should be the max size to get. Windows 98 won't recognize a drive over 20 gigs, IIRC. So you would have to use Windows 2000 or XP instead.
Here are three sources I use for old or used parts:
[link|http://www.computergeeks.com/|http://www.computergeeks.com/]
[link|http://www.netseller.com/|http://www.netseller.com/]
[link|http://www.pconramp.com/|http://www.pconramp.com/]
Edit: One other thing to do is zero wipe the 80gig drive. It may be full of junk or errors. Download Killdisk from [link|http://www.killdisk.com/eraser.htm|http://www.killdisk.com/eraser.htm] and run it on the 80 gig drive and then after killing the disk, reformat it and see if that fixes it. I had to do this with my 80Gig drive after I updated the BIOS to see the 80Gig drive and I had some of the errors that you had with the disk being empty or scrambled, etc.
Use the utility that comes with the hard drive to partition it, use no bigger than 20gig partitions for 98, or else it may not be able to read them properly.
Alternatively to the WD drive partition program, I was able to use KNOPPIX CFDISK to partition the drive, it handles 80gig and larger drives as well.
I went through something like that with a 160Gig drive, and then same thing with an 80Gig drive. I feel your pain.
Chances are the Quantum may be ok, but the signals from the WD confused the system. Try the Quantum by itself and see if you can access it.