Command to type in "run" to diagnose hard drive errors

Hi,

I am new to the group and hope that someone can help. About 15 months ago, my hard drive began having problems. Through an online search, I found a command that you type in "run" (after clicking "start") that allowed you to check activity of the hard drive.

Since we had the drive replaced, I cannot recall that command, nor can I locate where I obtained it 15 months ago.

If someone knows that command, please let me know.

Thanks.