I have an i5 2500K and idling i get around 45% CPU usage. This seems very high, is there anything I can do to lower the usage?
EDIT: Sometimes though it will drop to around 1% but it's weird how it spikes randomly.
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have you run a virus scan lately? check your background programs... things like skype will access your cpu for no good reason
check task manager and see which process is using your cpu.
Check task manager and download an Anti-virus program if you haven't already. I really like AVAST but there are a decent amount of free ones out there. I would also download Malwarebytes and run a scan for any Malware.