A full system scan runs an in-depth system scan that covers every area inside a computer. The area that a full scan covers includes: A hard drive Memory External devices connected to the system USB flash drives All the internal data Depending on the system memory, different programs, and hard drive space, a full scan can take hours to complete the full system analysis. On the other hand, a quick scan covers only common areas that include hard drive, system memory, temporary internet files, boot sectors, and system operating database. It will take a few minutes to complete the virus-detecting process in the limited areas of the computer. You can use it to trace Malware and worms in your system quickly, but it may not be able to detect other deeply seated malicious programs in your computer.