I have succeeded in Windows XP with the installation of a
"Hayes 336 FAX Modem"
by using the standard Windows XP driver for a
"Standard 33600 Modem".
The "Hayes" driver from Microsoft's XP database does NOT work with this Hayes modem, ( ha ! )
BUT, the STANDARD MODEM DRIVER for XP works just fine ! !
If you are having troubles with your modem in XP,
then why not try the "STANDARD DRIVER" for your modem type.
When other drivers, even from your own modem's manufacturer, have not worked, why not try the XP standard modem driver. It might just work !