Since Windows Defender comes by default for the protection of information in the operating system, any tools you get to choose to strengthen security in Microsoft Windows 8 will temporarily disable the above, which is due mainly to prevent there are a version mismatch and stability problems later on Windows 8. You can only install an anti-malware at once, something that is usually done in any version of operating system with which we worked. From the same Microsoft page, you can make the selection of the tool that is your preference since each meets the respective link to its official website with the respective explanation compatibility with Windows 8.