I'm having trouble installing the service. After lots of testing, here's what I've found:
I cannot install the FaxMan service (faxman4.exe -install) at all on my physical machine, running Windows 7 Enterprise, 64 bit.
For testing the problem, I then created two virtual machines using VirtualBox, one with Windows 7 Enterprise 64 bit and one with 32 bit.
On both VMs I can install the FaxMan service successfully only if logged in as Administrator (the actual user).
On both VMs I cannot install the service when logged in as any other user in the Administrators group.