My computer suddenly won't boot. IDE auto detection can detect the HD, but gives messages: "Primary master hard disk fail", and then "Disk boot failure, insert system and press enter". after booting with floppy, no hard drive appears. The hard disk was then taken off and connected to another computer, it was working ok. It sounds very strange. Is it a hardware or software problem?

according to an answer on this forum, maybe check connection and/or try without enabling floppy reader. i'd the same on a pc which didn't recognize hdd at reset (except when hardly stop)and it worked after unplugged/replugged floppy.Try it?

Was the hard drive connected to the second computer as primary or secondary drive?

If the HDD works ok on another computer fine then it sound like it could either be a problem with the cable you are using in the "bad" PC or the actual IDE controller on the motherboard, have you tried chaging the IDE channel on the motherboard and tried using different cables ? If you have then i sounds like it could be your motherboard ?? Hope this helps. Regards

Finally, it worked OK after changing another bus cable, although the unpluging/repluging floppy and changing IDE channel couldn't help. Many thanks to taxi, samdog and HP Man for your suggestions.

Unfortunately, the problem happend again. The computer hanged when I tried to shut down and the ctrl-alt-del didn't work. The same problem happed again when I reset the computer. This time, if the cable disconnected the CD-ROM, the HD couldn't be detected. It seems the resetting can damage the cable.