Event Viewer - System. The Network Security service terminated with the following error: The specified module could not be found. PC Powers

Event Viewer - System. The Network Security service terminated with the following error: The specified module could not be found. PC Powers Off

I have had a lot of viruses on my PC which I have removed. I seem to have developed a problem and maybe an important file has been removed as a false positive. I'm not sure. My PC (Windows XP Home SP3) randomly powers off. the last (and only) error in event viewer is as follows: