What happens is as follows: the connection drops during an online session for some unknown reason. When I attempt to redial, it says no dial tone. The device manager indicates that the modem is not functioning properly. I restart Windows; same thing.

The first time it happened I thought I had a failed modem, so I moved it into another computer where it installed and functioned as normal. So I moved it back into the original machine, in the same PCI slot it came from. No joy. I then wondered if the PCI slot was faulty, and tried it in another one. Again, nothing. I then put a different card in the PCI slot that originally had the modem (to establish for sure whether that slot was kosher or not), and both cards worked fine. No plug-and-play detect and install process, everything worked as if it had been there all along.

When it happened again last night, I simply swapped the modem and IEEE1394 cards between slots: problem sorted. As I said, this can't be a hardware fault because exactly the same problem has happened twice on two entirely different machines with completely separate components. Is there some registry section that defines which hardware devices are plugged into what PCI slots on the motherboard that got corrupted somehow, a BIOS setting that Windows could be conflicting with or an IRQ problem (there shouldn't be an IRQ problem with W2K on an ACPI motherboard, though)?

For the record, this machine has W2K service pack 3. The machine that had this problem previously was on SP1.

Answers on a postcard please...

Also, beware of installing service pack 3, as it changes the EULA (end user license agreement) to allow MS to do various questionable things to your machine without needing further permission from the user.
 

The modem is simply the cheapest one that ebyuer.com had, and it lists on the device manager as 'Zoom 56K PCI Faxmodem'. If this happens again I'll try the driver first.
 

Be sure your drivers are compatible with W2K. Older ones are not.

Word of caution: Be sure to physically remove the power cord from the power supply before you yank and/or install the modem. There is power applied to the MB even if the power switch is turned off. If you fail to physically disconnect the power cord, you could blow the brains out of the mother board, modem, and possibly other hardware.

There could be a distinct possibility that might have already happened to you.

My gut feeling is that this is a weird W2K glitch. I don't think it's a driver issue because that modem has worked happily under W2K for six months before the problem happened. If it happens again, I'll try the driver route first.