The Windows CPU alarm is activated when the average CPU utilization of the system (taken over a specific number of refresh intervals; the default is four) exceeds a threshold. Sustained high CPU utilization can adversely effect the performance of the system.
When this alarm is current, you should:
Look at the Summary page on the Memory drilldown to see if there is a high paging rate. High paging rate can cause inflated CPU utilization.
If this is the case, adding more memory to the system may overcome the problem.