Sounds like the classical IRQ sharing problem. Several devices may share the same IRQ and a couple of them are in conflict. Right click on My Computer and bring up the hardware manager and see what devices are sharing the same IRQ's with your 56K modem.

Sampson, thanks for the reply.
 
>Sounds like the classical IRQ sharing problem.<
 
I think you've got it.
 
The 56k modem uses IRQ10 (I/O range E200-E2FF), and the properties says that there are no conflicts. The USB modem appears in the device list as a network adapter USB ISDN TA, for which no IRQ is listed.
 
However, I discovered in the device manager that under 'USB controllers' is an entry for 'VIA Rev 5 or later USB Universal Host Controller' which also uses IRQ10 (I/O range 12000-121F) (again it says there is no conflict!).
 
This could also explain the fact that there is much cooling-fan activity when the USB modem is plugged-in (I rarely heard the fan until I got this modem!). It seems to me really bad configuration that the internal modem should have the same IRQ as the USB controller!
 
So, now I think we've cracked the problem, how can I change the IRQ for either the 56k modem (preferably) or the USB port?
 
Many thanks,
Alan

Actually, there is not much you can do about it. If this were a desktop, you could try pulling the modem out and putting it into a different slot. That will sometimes allow XP to reassign the IRQ. Since this is a laptop and the modem is built in, that idea won't work. It may be possible that your laptop has a later bios and by flashing it, this could reassign the IRQ or there may be a firmware upgrade on the modem. I think that Hayes is out of business, but there may be a software upgrade that could change the IRQ (though I doubt it.) It is a shame that there is a conflict. Your laptop maker probably never considered that the USB port would be used for another modem. I wish I could give you a solution. If I run across something, I will get back to you.

Samspon, thanks for the reply.
 
>>I think that Hayes is out of business,<<
Really? They are still selling loads of stuff here in the UK.
 
>>... but there may be a software upgrade that could change the IRQ (though I doubt it.)<<
I'll look into it.
 
>> If I run across something, I will get back to you.<<
Many thanks. I'll contact the laptop manufacturer and see if they have any ideas.
 
Regards,
Alan

or you could manage your IRQs from the bios instead of having XP do it.

trilliansucks, thanks for the reply.
 
>>or you could manage your IRQs from the bios instead of having XP do it.<<
 
I presume managing IRQs from the bios involves looking at the setup when the laptop boots-up, but how can I do it from XP?
 
TIA
Alan

Generally, as the computer boots up, you can hit the Del key or the Esc key (and since it is a laptop you may have a key sequence) before the computer gets into windows. Some laptops simply won't let you get into the Bios. If yours does, then a set of screens comes up. Don't change anything your first go around. Write down the values you find in case you accidentally change something. That's the Bios; that's where you can change IRQ's. With laptops it is probably pretty limited, but it won't hurt to look.

Here's something else that could help free up some resources here:
 
1) If you don't use a serial mouse then disable both the COM1 and the COM2 ports in the system BIOS.
 
2) If you don't use a parallel printer, then you can also disable the LPT1 port in the system BIOS.
 
This will essentially free up 3 IRQ's for and base addresses for you to use. Hopefully XP then can reassign to the proper, non-shared IRQ's and everything will work.
 
You have d/l the latest device drivers for the onboard modem I presume ?!?