Malicious Or Just Windows It Is

I ran LiveUpdate on Norton Systemworks 2003. It updated LI only, and asked me to reboot. I did. I also, following some advice I found on TSG during a Google search, switched the Speed Disk service to "manual", as it was causing my HD to work overtime. As it was nearly 1am by then, I went off to bed. My system is protected by ZoneAlarm, Spybot resident, Norton Systemworks with auto updates. I do, however, have a broadband connection and leave the system on at night. I'm running Windows 2000 Pro. Monitor hadn't powersaved. Rightclick had stopped working, clicking on anything in my startbar had no effect, except "start", but that would only bring up the 4 items that would be above 'programs', and I couldn't click on them either. So, I rebooted, and everything worked fine. I was on the system for around 1/2 hour,I went downstairs for breakfast, and when I returned I found it in the same state.