when XP saw that there was another Op Sys on the disk??? Did it ask if you wanted to install XP on the same partition or????
Possible problems is because proprietary computers such as Compaq's and especially the older ones had data stored on a hidden partiton telling the system what hardware it has and has the drivers. TheBIOS may be confused by the different drive.
Can you boot up with a 98 boot floppy?
Can you get into the BIOS to boot from the floppy first if it isn't already set that way.
Did the drive show on the boot screen????
I bought a used Compaq Deskpro P3 700MHz without a hard disk. I plug it with my hard disk from my old pc P2 233MHz MMX running on Windows 98 and when turned it on, it gave an error message - Non system disk. When I ran the setup during boot up, it saw the hard disk and when I ran Windows xp install, it detected the hard disk and saw it had another OS in it. Any thought what's wrong here?