http://pcpitstop.com/spycheck/SWDetail.asp?fn=keyhook.exe
Vendor contains: Silicon Integrated Systems
Product contains: SIS Super VGA keyboard daemon
Recommendation
Usually should not be disabled. See below for more information.
To get control over your running programs we suggest WinTasks 5 Pro
Purpose
Keyhook.exe is used to allow multimedia keys on Acer multimedia keyboards to function correctly. If you stop this process all of the 'normal' keys on the keyboard should still function, but the multimedia keys will not. Only stop this process if it is causing instability to your system.