Yesterday my office machine was working fine. This morning I accessed it from home. It had restarted after Windows automatic update overnight. Now CPU usage is 100%, hardly any of it in System Idle Process. It's worst when iexplorer is running (40-60% of CPU usage). Windows task manager takes a bigger chunk than usual. Forget about doing useful work.

Whan can be the explanation? What can be done about it?

TIA,

Alex