Once in a while my XP machine would auto shutdown immediately after booting up. I would log in to Windows and if I didn't wait for all the services to start it would go through the shutdown process and power off. Now it is doing it every single time, even if I don't login. After 30 seconds or so it will popup a window with "Windows is now shutting down". I can boot into safe mode with out a problem. I checked MSCONFIG and stopped everything I didn't need from starting up, but the problem continues. There are no errors on startup, chkdsk, etc, so I don't think it is a hardware issue. It appears to be some service that is starting up. I suspect it might be the TrippLite PowerAlert software that I had installed to manage my UPS. This software has never worked properly and I had recently uninstalled it.