Client called with an XP Home SP2 machine that would hang at "welcome" login screen, without even displaying user account icons. Same behavior in safe mode. No luck with "last known good configuration". So I repaired installation from recovery console by manually copying restore point registry hives to system32/config folder, and system works fine now. But I noticed that in the documents and settings folder, there are now a whole series of new folders that were apparently created every time the system hung. They are labelled "LocalService.NT Authority.XXX" and "NetworkService.NT Authority.XXX" where the XXX are sequentially numbered 001, 002, 003 and the time stamps on the folders are consistent with one of each being created at each unsuccessful boot. There are also two folders "LocalService" and "NetworkService", that have been there for a long time, and there are two folders, labelled "LocalService.NT Authority" and "NetworkService.NT Authority" (without the .XXX) that have time stamps a little earlier in the same day (i.e. BEFORE the machine started locking up). Client had installed Norton Internet Security 2005 that day, which may have created those folders, and may have been the event that triggered everything else, but client wasn't sure of exactly what happened when. Client had previously had Norton Anti-Virus 2003 on the machine and did not uninstall and purge remnants of it from the machine before installing the new product, which in my experience with Norton products has caused many prior problems.
Based on above, can anyone diagnose why the system wasn't booting properly? If I run into the problem again, is there a quicker fix than restoring the registry? (which took about 1/2 hour)