Hitman Pro is a second opinion scanner, designed to rescue your computer from malware (viruses, spyware, rootkits, etc.) that have infected your computer despite all the security measures you have taken (such as anti virus software, firewalls, etc.). Just relying on a single vendor is not sufficient to completely protect you. You do need a second source to make sure you are secure. Hitman Pro is designed to work alongside existing security programs without any conflicts. It scans the computer quickly (less than 5 minutes) and does not slow down the computer (except for the few minutes it is scanning). Hitman Pro does not need to be installed. It can be run straight from a USB flash drive, a CD/DVD, local or network attached hard drive.