Originally posted by another user
Microsoft allows users to freely download, install and use Microsoft Security Essentials on an unlimited number of their computers in their household which has a genuine copy of Microsoft Windows. Microsoft Security Essentials checks for genuineness of the operating system during and after installation. If the operating system is found to be not genuine Microsoft Security Essentials may cease to operate after a period of time during which user receives notifications.[2]
Microsoft Security Essentials software license agreements also denies user the right to reverse-engineer, hack, decompile or disassemble the software or to publish or disclose the results of benchmark tests of this software to third parties without written approval from Microsoft Corporation. It also does not endorse the commercial use of this product in business environments or government agencies