The windows d drive has been formatted. When I try to partition I see only
hda which I think is The windows "C" drive which I do not want to change.
How do I get to hdb where I want to load Linux on?

1st. Please, Please, consider using a modern distro. Support for RH9 ended in 2004 and RH7 was a couple of years before that. RH9 was the last of the straight RH line, they switched to RHEL (Red Hat Enterprise Linux) and are now on RHEL 5.2. RHEL charges to install/update but Centos is RHEL with the logos removed. Centos is free to download/update and will run RHEL binaries.

Are you just using ide (pata) drives or do you have sata drives too?

Since we are talking Win98 here, you might want to reconsider that suggestion. I'm quite sure the hardware is dated so the new RHEL/FC/Centos is probably a bit too heavy for it. Chances of having SATA here are zero. I guarantee it.

Moving along, the way drive naming works in Linux is such, where in your case an IDE drive is hdYX, where Y is the drive number on the bus, starting with primary master, and X the partition number in the partition table.
As I remember 7.3 had graphical partitioning options during install, and it should say what file system the partition uses.
If you can't figure out which one is the Windows partition and which one you are supposed to install Linux on, go back to Windows and completely delete the D partition. You will see it as empty space in the RedHat 7.3 installer, and you will have an opportunity to format it with ext2/ext3 for use with Linux. Your "D" partition is probably FAT32 and not very suitable for Linux anyway.

Ask more specific questions if you want further explanation.

My PIII (which started with 98) runs Centos5.2 just fine. It also has a sata drive on it now. The min requirements are a Pentium (1) with at least 256mb ram (512 would be much better).

Run fdisk, then tag hdb as a Linux partition (i forget the no.)

Maybe you have two drives, and the second "drive" was D:\.
If that is the case, to be absolutely certain you don't lose data, why not disconnect the Windows one and try to see if RH will see the drive.

If you have made partitions in your single "drive" as D:\, you won't see it as hdb, rather hda<number>
hda -- Primary Master IDE
hdb -- Primary Slave IDE
hdc -- Secondary Master IDE
hdd -- Secondary Slave IDE

Also please consider Xubuntu or DSL for a old system.