Hello all, Thanks to everybody who took care of my problem... I have performed some extra tests for actual problem determination with ISO generation, in my case. Here are the results : If I perform an update (say SP3 over native XP) I have no problem whatever application is running : LAN, antivirus (AVAST), anti-spy (resident SpyBot), anti-adware (Ad-Watch live) and anti spam (SpamPal). To be able to generate ISO, when I add drivers (nVidia) and/or automation to the above, I need ONLY to stop "Ad-Watch live" (from Ad-Aware) . Why ? I have to add that when ISO generation stops : the system is not frozen nor Nlite : I can still use Cancel and Abort commands from the Nlite window an extra file named "setupreg.hiv.log" is created in the I386 folder both files setupreg.hiv (present in native XP I386 folder) and setupreg.hiv.log are locked until reboot (no way to edit, rename or delete them) Conclusion : the tip to disable all security SW given by johnhc did the job, even if, in my case, only one was the culprit.