For students and home users, we recommend using Windows Defender, which is already built into Windows 10 and Windows 8.
For Windows 7, we recommend using Microsoft Security Essentials. Download Microsoft Security Essentials from their site: https://support.microsoft.com/en-us/help/14210/security-essentials-download
University-owned laptops and desktops are already installed with the enterprise version of Windows Defender.
If you're a student and have concerns that you may already have malicious software present on your computer, please refer to this Knowledge Base Article - I am a student, how can I check for or remove viruses, spyware, and other junk from my computer?