Software & Apps Windows Keep Your PC Virus Free With Microsoft Security Essentials Schedule a scan during downtime By Gilberto Perera Writer Former Lifewire writer Gilberto J. Perera is a PMP and Six Sigma professional with more than 15 years of technology education experience and editor-in-chief of GilsMethod.com. our editorial process Gilberto Perera Updated October 26, 2019 Lifewire / Gilberto Perera Windows The Ultimate Laptop Buying Guide Tweet Share Email Once you've performed a manual virus scan or two, you will most likely want scans to be an automatic process with little or no input on your part. Fortunately, Microsoft Security Essentials (MSE) allows you to schedule virus scans on your Windows PC. In this guide, we will show you how to set-up MSE so that you can have virus scans run automatically and stop worrying so much about your computer's safety. Instructions in this article apply to Windows 7. How to Schedule Virus Scans Select Start, point to All Programs, and choose Microsoft Security Essentials. Select the Settings tab in Microsoft Security Essentials. Select Run a scheduled scan on my computer (recommended). Select the type of scan. There are three types of scans that you can schedule: Quick — This scan will be quick and only scan the sections most likely to contain malware. That means MSE may not be able to find more pernicious viruses and malware lurking deep in your computer.Full — The full scan is the best option if you have not done a security scan on your Windows machine in a while. It is also a good option if you are scheduling the scans to take place when you are not using the computer.Custom — This option allows you to set specific parameters like where you want to scan and the level of the scan. This is a great option if you have an external hard drive or a memory key you wish to scan along with your computer's regular drive. Select a frequency. The options are to do it every Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, Sunday, or daily. Once a week should suffice for most PCs; however, if there are a lot of people who use the computer, or if you spend a lot of time checking email and surfing the web, it may be a good idea to run a scan every day. Select a time. The Around dropdown menu provides you with a list of every hour in the day. Select the time that best suits your schedule. If you don't plan to use the computer past 10 PM, for example, then schedule the scan to take place shortly after that time. Once you've determined the type of scan and when you want to run it, the next step is determining whether or not to enable the following options: Check for the latest virus and spyware definitions before running a scheduled scan: When selected, Security Essentials will check to see if there are any additional spyware definitions ready for download before beginning a scan. This is a critical setting, and it is absolutely recommended that you enable it.Start the scheduled scan only when my computer is on but not in use: If the scan is scheduled for 10 PM, but you are still using the computer, the scan will not begin until the computer is idle again. A very nice feature that makes sure any virus scans don't interfere with your use of the PC.Limit CPU usage during scan to (select percentage from the drop-down): This is the option that helps determine how many resources will be dedicated to scanning the computer for malware. The lower the value the less of an impact the virus scan will have on the work you are trying to accomplish on your computer; however, a lower value will also slow down the scan. If you increase the amount of resources available, on the other hand, the scan will take less time but carrying out tasks on your PC will take that much longer. You should only use the CPU limiting option if you plan to use the computer while the scheduled scan is in progress, otherwise, uncheck this option. Once you've made your selections, select Save changes. You may be prompted to confirm the changes by User Account Control. Select Yes to confirm. Once it's all set up, Microsoft Security Essentials will scan your computer at the scheduled times you assigned. Even though you have a scheduled scan running either every day or on a weekly basis, it's still a good idea to run a manual scan every now and then to make sure your PC is running smoothly.