Having used Nlite - absolutly a brill prog - and customised several things, I have a little problem which I can not figure out. So. My install of Win XP SP3 installs nicely onto a (and I think this is the clue) system with a single CPU. But.... when installed onto a dual CPU the file "ntoskrnl.exe" is not the one I have customised ! when replacing it with mine using replacer.cmd all goes well untill I reboot and bang not boot. Now before you jump to conclusions the file is fine it works - known and tested. Also the file ntoskrnl.exe on this dual CPU is smaller. My Question is :- How does windows installation decide and then create/install this different ntoskrnl.exe and where does it come from.