Now it's the sound. Hardware is there but...

Can modem settings affect this? When I try playing with sound, I am informed another application may be using it.
Also, after having reloaded indows, I seem to have two Window files, one named Windows, th other Windows 00.0

Need expert (free) advisor!

Modems, Sound Cards, and Network Cards, are renowned for causing IRQ conflicts.

If you have an alternative available slot, try the sound card in there. This will force Windows to allocate a different IRQ.

Also, check your motherboard manual. It may give advice on which slots share IRQ's.

Another thing to check under system, device properties is that the system is not trying to use the modem as the sound device, if there are any sound devices that you dont recognise you could tell the system not to use this device (ie disable it) and if it causes a problem all you have to do is re-enable it.
But I agree that Modems and sound cards are notorious for causing problems on a PC.