Can you trust your PC?
Admirable, if you answer with "Yes".
But perhaps even you are curious why your hard disk LED is sometimes flashing. Or why the CPU fan gets louder even if you're not doing anything.
The free software "What's my computer doing?" tells you why. It shows all programs (with details!), that are accessing your hard disk or using the CPU. Furthermore you have the option to close these programs or even uninstall them.
Windows 8, 7, Vista, 2003, XP