I have a rather old PC with the specs listed above that has 2 hard drives installed. The first hard drive is a real old 3.7GB Quantum Fireball and the 2nd one is a 40GB Seagate drive that's about 3 years old. I removed the motherboard from this PC and installed another motherboard that I wanted to test inside the ATX case. I left all the hard disks, CD burner, and floppy drive in (I never hooked them up when testing this other board). After I was done, I put the original motherboard back in, and made sure all the connections were correct. When I turned the PC on, it came on as usual, but the 40GB HD was no longer listed in the POST. I went to the BIOS, and it said Not Installed. Everything else was listed. When the boot selection came on, I selected Windows 2000 Professional expecting to see an error, but it booted completely normally. Any ideas why this happened? I never changed anything!

Your subject description fades off--". . .still works in sa. . ." Safe mode? Anyway, if the bios isn't seeing the 40 gig and your OS is on the 3.7 gig it should still boot up OK. (But then I wouldn't expect it to be seen in safe mode, if that was your meaning.) I'm wondering though, how you got a P-I to see a 40 gig. Is it a super socket 7 motherboard? I think that's the only one that may see a drive that large. Or did you have to install a drive overlay for it to be seen? An overlay could require a different cmos ID for the drive. Or is it connected to an ATA card? In that case it's not going to show in cmos anyway. I've noticed when moving around motherboards the cmos often gets cleared. Maybe that's what happened and you lost the configuration for that drive. If the date was wrong or you got a message on first boot about needing to go into bios setup, that's the likely reason. I know you said everything's connected right but check the cable again, especially if the drives are on different IDE channels. More than once on a cramped motherboard I've misaligned the cable.

P1 PC's very likely have a 8GB Hard Drive Limit, maybe less. If the 40GB Drive uses a Disk Drive Overlay Software Solution, the DDO will ignore BIOS setting.

Thanks so much for the replies. My subject was supposed to be "HD not found, but still works in same PC". I've already checked the cables 4 or 5 times and they're ok. The 3.7GB and the 40GB are both connected to the same cable, the 3.7GB on Master, the 40GB on slave. Windows 2000 is installed on the 40GB hard drive, Windows 98 SE on the 3.7GB, although I never use Windows 98. I didn't get an error about needing to go to the BIOS. I actually don't remember how I managed to get the 40GB drive to work, I think the Windows 2000 setup just miraculously saw all of the 40GB. I remember having problems getting the DDO installed (the Seagate CD would always hang when trying to install it). The hard drives are directly connected to the motherboard, no IDE cards are used. I'm not sure what socket it is, it's an old Gateway that was about to be thrown away when someone picked it up and brought it to me. I just wondered what could have caused this phenomenon. The computer still works like new although the second HD isn't in the BIOS, and my whole 40GB drive is still being recognized by Windows.

So it's booting from a drive the bios doesn't recognize? There's 2 IDE connections on the motherboard--primary and secondary. Normally you'd have the hard drives connected on the primary although they'll work OK on secondary. Could you have reconnected them to the secondary? Then in the bios it would show the Not Installed for drives on the primary. I don't know how you got the 40 working but maybe you should leave it alone since it is booting up OK. It may be one of those cases where changing the settings will screw up everything.

"So it's booting from a drive the bios doesn't recognize?" Literally, yes. I've never seen it before. Actually I never disconnected the IDE cables when trying that other board, I left them connected to the board but just disconnected them from the drives. I guess I'll leave it alone before I really mess it up. Thanks for the replies so much.