For one thing, W98 will not install on anything other than a C: drive hooked up to the Primary IDE controller, so if the new drive that you want for a dual boot is actually going to be on D: drive, you're barking up the wrong tree for that version windows.
I would try this....disconnect your XP harddrive temporarily, then get the new drive hooked up on the Primary IDE controller as the Master. Make sure your cdrom is either still connected as the slave on that cable or as a master/slave on the Secondary IDE controller so you can get W98 installed on it.
Make sure that you Fdisk/format the new drive...then install Windows98. Get all your hardware drivers and the internet set up, including antivirus for this version windows.
Once you have W98 set up pretty much the way you want (you can install various programs later and detail the desktop settings the way you want them), keep W98 as the Master drive, then hook up the XP drive (if on the same cable, you can jumper them both to be cable select, but use the end connector on the W98 drive and the middle connector for the XP drive).
Now...you won't get a choice yet about which one to boot from, so it's a toss up of which one will show up first since both are bootable, but if it turns out to be W98, you may not be able to see the other drive due to W98 being FAT32 and XP is probably formatted as NTFS. XP can see W98, but not the other way around.
If you can't get to the XP drive because it boots to W98, the boot.ini file has to be edited to allow for dual booting. Whether you have to edit the one for W98 or XP is a shooting match as well, but perhaps you can still edit BOTH by using a dos program that will allow you to access NTFS files (link later if you need it), but you can get lucky by booting up with the XP cd and getting into its Recovery Console to do the editing for that one.
Here are some various ways of editing the boot.ini files (obviously "whistler" referred to here is XP):
Instructions on how to alter the Boot.ini file for dual booting:
http://support.microsoft.com/default.aspx?scid=kb;EN-US;q291980
RECOVERY CONSOLE FOR XP:
The bootcfg command is a Microsoft Windows XP Recovery Console command that manipulates the Boot.ini file. This command has a function that can scan your hard disks for Microsoft Windows NT, Microsoft Windows 2000, and Windows XP installations, and then add them to an existing Boot.ini file or rebuild a new Boot.ini file, if one does not exist. The bootcfg command enables additional Boot.ini file parameters to be added to existing or new entries.
To use the bootcfg command, start the Recovery Console with the Windows XP CD-ROM, and then click Recovery Console . Or, install the Recovery Console locally, and then select the command from the Boot menu.
The bootcfg command and its uses:
The bootcfg /default command sets the default operating system option in the Boot menu (the command selects the operating system entry automatically).
The bootcfg /add command scans the computer for Windows NT, Windows 2000, or Windows XP (if dual booting) installations, and then displays the results. From this location you can add an installation to the Boot menu.
An example of the message that may be displayed:
Scanning all disks for Windows Installations
Please wait, since this may take a while...
Total Identified Windows Installs: 2
[1] C:\Windows
[2] D:\Windows
Select installation to add: (select a number)
Enter Load Identifier: (Custom description for an operating system loading from the Boot menu)
Enter Operating System Load Options: (that is: /fastdetect)
This process adds a new entry into the Boot menu. When you add an installation, the bootcfg command also makes the installation the default operating system boot entry.
The bootcfg /rebuild command scans the hard disks of the computer for Windows NT, Windows 2000, or Windows XP installations, and then displays the results. You can add the detected Windows installations.
An example of the message that may be displayed:
Total Identified Windows Installs: 2
[1] C:\Windows
Add installation to boot list? (Yes/No/All):
Enter Load Identifier: (Custom description for an operating system loading from the Boot menu)
Enter Operating System Load Options: (that is: /fastdetect)
[2] D:\Windows
Add installation to boot list? (Yes/No/All):
Enter Load Identifier: (Custom description for an operating system loading from the Boot menu)
Enter Operating System Load Options: (that is: /fastdetect)
The bootcfg /scan command scans the hard disks of the computer for Windows NT, Windows 2000 or Windows XP installations, and then displays the results.
An example of the message that may be displayed:
Scanning all disks for Windows Installations
Please wait, since this may take a while...
Total Identified Windows Installs: 2
[1] C:\Windows
[2] D:\Windows
The bootcfg /list command reads the Boot.ini file, and then displays the operating system identifier, the operating system load options, and the operating system location (path).
An example of the message that may be displayed:
Total entries in boot list: 2
[1] Microsoft Windows Whistler Professional
Operating System Load Options: /fastdetect
Operating System Location: D:\Windows
[2] Microsoft Windows Whistler Server
Operating System Load Options: /fastdetect
Operating System Location: C:\Windows
The bootcfg /redirect command enables redirection in the boot loader with the configuration specified as port and baudrate. This command is used to enable the Headless Administration feature.
An example of this command:
bootcfg /redirect com1 115200
bootcfg /redirect useBiosSettings
The bootcfg /disableredirect command disables redirection in the boot loader with the configuration specified as port and baudrate. This command is used to disable the Headless Administration feature.
You can also modify the Boot.ini file in the Windows XP graphical user interface (GUI):
In Control Panel, double-click System .
On the Advanced tab, click Startup and Recovery , and then click Settings .
Under System Startup , click Edit .
You must save your changes, and then click OK to to leave the Startup and Recovery window before the changes to the Boot.ini file are seen.
Click Start , click Run , and then type: msconfig to start the System Configuration utility.
Click the Boot.ini tab.
TONI