This is one of the weirdest I've ever come across. I'm fixing up an old Dell XPS D333 for my mother-in-law. The machine which I had previously fixed up for use in our family had run absolutely flawlessly for 2 years. However, upon installing a pair of clean hard drives from other machines, I can't get the system to boot to a command prompt. Each time I boot with a Win 98 Startup disk, I get either of two errors..."I/O error. Replace the disk and hit any key" or "No Operating System found". I've tried new floppy drives, several different boot disks made on other machines, swapping and removing memory modules, swapping the hard drive boot order, trying completely different hard drives, but I can't get the thing to boot to a command prompt. I've searched the web for weeks trying to find a similar problem, but haven't been able to find anything to match it. I also tried installing XP from a CD boot. It booted and ran the setup files for most of the cycle, but about 50% through the install I got an XP error about "Fatal I/O error has occurred. Setup has aborted" or something to that effect. If anyone has ANY idea about this or has seen something similar, I would certainly appreciate your input. Thank you.

Disconnect the hard drives and try it. You might have a cableing or plugging error.

Hi have you checked the boot order in the bios? hdd needs to be set last.
As far as XP comp might be to slow.

During XP setup. Hit F6 when prompted to do so. Setup will continue on to a certain point and then it will allow you to load the IDE controler drivers for the motherboard. They need to be on a floppy disk, because it will search your A: drive when you go to load the drivers.