Ok, a quick description, and then you can ask questions where I don't make thing clear:

1) Install XP on the drive. You may already have it installed

2) Use Partition Magic 8 to add a new primary partition before the XP partition. XP should still boot.

3) Install 98 on the drive, getting it to use the new partition (it will probably not give you a choice). Use thet boot from CD method of instalation. After that you wont be able to boot XP for a while

4) Run 98 and start XP installation from the CD. Don't use the boot from CD method. Run the installer from within 98. That works by copying files to the 98 partition, and then altering the boot block to dual boot. One option from the dual boot is to complete the XP installation. Don't let it do that. Let it reboot, but choose to go back into 98.

5) Edit boot.ini. Look for something like

1multi(0)disk(0)rdisk(1)partition(1)\WINDOWS="Microsoft Windows XP Professional" /fastdetect

Change the partition. Not sure exactly what the change should be 0->1 1->2 1->0, but its not too risky to experiment. If its looking uncertain, then first delete the files that the XP installation copied to the 98 partition. That will stop it from completing.

I second that!

Thank you very much,Glidos.
Two points,please,both about 5) of your post:
Must I change,after the word partition,"(1)" to,let us say,"(0->1)",or just to " 0->1"?;
And,that shall be done with,or without,the WinXP CD in the drive?
Best regards,

Where it says "partition(1)" change it to "partition(0)". Or it might be 0 already and you have to change it to 1.

Also the words wont be "Microsoft Windows XP Professional". They will probably be something like "Continue Installation of Windows XP". You can change them to whatever you want to see on the dualboot menu.

Good point about XP CD. Once all the files have been copied in step 4, it is probably best to remove the XP CD. That will help to ensure that the process doesn't complete.

If you did accidently complete the second XP installation it would only mess up the W98 partition a bit. So you could just go back to installing 98 afresh.