Installing Windows XP Professional as in inplace "Upgrade" on top of WinFLP converted the install to a Windows Embedded edition that had working dialup support - I was primarily interested in getting both dialup and ICS working on the machine, but quit after ICS failed to function correctly.
Alternatively, you may also try the following command, which I found was required to enable Windows Firewall working - it has a WMI dependency, perhaps dialup does also. It's easier to uninstall (check wbemoc.inf to be sure) by changing the install part to uninstall:
WinFLP > WinXPe with dialup
Installing Windows XP Professional as in inplace "Upgrade" on top of WinFLP converted the install to a Windows Embedded edition that had working dialup support - I was primarily interested in getting both dialup and ICS working on the machine, but quit after ICS failed to function correctly.
Alternatively, you may also try the following command, which I found was required to enable Windows Firewall working - it has a WMI dependency, perhaps dialup does also. It's easier to uninstall (check wbemoc.inf to be sure) by changing the install part to uninstall:
rundll32.exe setupapi,InstallHinfSection WBEM 132 %windir%\inf\wbemoc.inf
(from http://windowsxp.mvps.org/repairwmi.htm)