High CPU Usage by "SYSTEM"

High CPU useage (50-60%) by "system" especially when "system interups" is also abnormal is usually caused by a driver problem.

Before you try anything, force the computer into "Sleep" mode and reopen. This can resolve problem with ACPI.sys (power mgmt).

If you need to further investgate the cause of high CPU useage LatencyMon is a tool that can be used to zero in on exactly which driver/system is the cause.
It can be downloaded at http://www.resplendence.com/latencymon