fax server mit hp officejet5615

i have a big problem

server: opensuse 11.1 with hp officejet 5615 (usb). clients 2 xp-home

file-, printserver (samba) and scanserver (sane) work fine. with hptoolbox i can send faxes from my server. but i found no way to send faxes from the xp clients.

hylafax always asks for a modem but i have none.

if there is any help, out there i would be grateful