I recently went out and bought a new computer system that I built myself. I also have a 250G S-ATA Seagate Harddrive that had a previous installation of WinXP Pro on it so I assumed it was just a matter of switching it out of my old system and putting it in my new one. However upon installing the hard drive WinXP refused to install, so I booted from the XP install disk and erased my harddrive and started a new installation of XP Professional, however I now get an error stating there is no installed harddrive, however I was able to install Win98 SE and it recognizes the harddrive just fine with no problem at all so I thought I should be able to install WinXP from 98 as an upgrade no problem, but the same problem keeps popping up. Any help with this would be greatly appreciated because I have a lot of hardware/software that is incompatiable with anything but WinXP.

Most info I see on changing Mobo's or HDD's requires a repair install of XP.

Here is a good guide to that process:

http://michaelstevenstech.com/index.html

As others have mentioned just do a Repair Install on your XP drive.
You might need to call the Microsoft Activation Center though as there
will be so many changes that WPA will likely require a reactivation.
However if your original install on the old drive was over 120 days ago
then you may not have to call the center and Activation will simply
progress normally.

More threads here:

microsoft.public.windowsxp.general