To delete unnecessary files on a hard disk use?

1. Open the Disk Cleanup by clicking Start, point to All Programs, point to Accessories, point to System Tools, and then click Disk Cleanup. Disk Cleanup will then calculate how much space you will be able to free on your hard drive.

2. Select the files by clicking the check box that you would like to delete (e.g. Downloaded Program Files and Temporary Internet Files) and click OK.

the answer to your question would be something called hertz. the unit of measurement called a hertz, which is one cycle per second, is used to measure clock speed. within one cycle, your computer processes, refreshes, or updates itself to the changes that it is going through. in the case of computer clock speed, one hertz equals one tick per second. the clock speed of computers is usually measured in megahertz (mhz) or gigahertz (ghz)