Difficulty: Moderately Easy
Step1
Head to the "Lavasoft" website and download the free version of Ad-Aware. The Pro, Plus and Enterprise versions also allow you to scan on start up, but the free version's good enough for regular home users.
Step2
Look for Ad-Aware's desktop icon and double-click it to launch the program.
Step3
Open the "Settings" menu by clicking its tab in the menu on the left side of the main program window.
Step4
Switch to the "Auto Scans" tab. It's the third tab, in between the ones labeled "Scanning" and "UI."
Step5
Find the "Scan on Windows Startup" field near the bottom of the screen. It contains the three auto scan choices available to you.
Step6
Select the type of scan you want Ad-Aware to perform when your computer boots up. The Smart Scan is short and only checks your machine's most sensitive locations for spyware, while the Full Scan sweeps your entire computer.
Step7
Press the "Save" button to lock the changes in. Ad-Aware will now run your selected scan each time Windows starts up.