The Schedule Type (two sections above the Start Time section) should be weekly, and just check the Friday box. Leave the Start Time as Run once at that time. In the Options section at the bottom, you can click or clear the check box for "Run missed task" to indicate if you want it to run when the computer is turned on after missing the task. If checked, then scan will run whenever the system is turned on, not just on Friday. The "minute delay" setting after the Run missed task checkbox is to allow Windows to get fully loaded before the scan starts. Leaving it 0 means the task will start right away.