OK, here is fully working solution.
Create VistaPE using Winbuilder (include what you want in it)
Do not create ISO, as we will need to adjust the .wim file
I could not be bothered to create script for Winbuilder for Converter, so will describe the manual steps taken:
\- mount wim for read/write access (imagex or even easier the Gui-Imagex wrapper.exe)
\- open registry on your PC (I used W2K3, should works also on XP) & load hive
"mountpoint"\Windows\System32\config\system as SYSTEM_00
\- import reg file (text below) to the registry
\- copy VSTOR2-P2V30.SYS to mountpoint"\Windows\System32\drivers
\- (optional) copy serviwin.exe (from http://www.nirsoft.net/utils/serviwin.html) to "mountpoint"\Windows\
\- unmount the image
-copy VMWARE-CONVERTER to ie Winbuilder\Target\VistaPE-beta\Programs\ (so it is accessible in VistaPE session - that can also be on USB key etc, as VistaPE does allow it - one of the reasons to use it!)
\- create ISO in Winbuilder
\- boot from the ISO (or CD if written to)
\- from command prompt run "net start vstor2-p2v30" or use serviwin to start this driver/service
\- from command prompt run "VMWARE-UFAD ufa.xml" and then "converter -boot"
Runs perfect, no questions asked
CUT HERE
\----
Windows Registry Editor Version 5.00
\[HKEY_LOCAL_MACHINE\SYSTEM_00\ControlSet001\Enum\Root\LEGACY_VSTOR2-P2V30]
"NextInstance"=dword:00000001
\[HKEY_LOCAL_MACHINE\SYSTEM_00\ControlSet001\Enum\Root\LEGACY_VSTOR2-P2V30\0000]
"Service"="vstor2-p2v30"
"Legacy"=dword:00000001
"ConfigFlags"=dword:00000000
"Class"="LegacyDriver"
"ClassGUID"="\{8ECC055D-047F-11D1-A537-0000F8753ED1}"
"DeviceDesc"="VMware vstor2 driver"
\[HKEY_LOCAL_MACHINE\SYSTEM_00\ControlSet001\Enum\Root\LEGACY_VSTOR2-P2V30\0000\Control]
"\*NewlyCreated*"=dword:00000000
\[HKEY_LOCAL_MACHINE\SYSTEM_00\ControlSet001\Services\vstor2-p2v30]
"ErrorControl"=dword:00000001
"Start"=dword:00000002
"Type"=dword:00000001
"DisplayName"="VMware vstor2 driver"
"ImagePath"="SYSTEM32
DRIVERS
vstor2-p2v30.sys"
\[HKEY_LOCAL_MACHINE\SYSTEM_00\ControlSet001\Services\vstor2-p2v30\Enum]
"0"="Root
LEGACY_VSTOR2-P2V30
0000"
"Count"=dword:00000001
"NextInstance"=dword:00000001
\----
CUT HERE