(Microsoft security essentials) this is a free antivirus protection program, it does have a paid verso but the free one is not a trial an i do believe it comes pre=installed with certain new windows 8 PCs because i recently got a new windows 8 Toshiba an it was pre-installed, if you do not have a anti virus or keep returning your comp. to factory default for the free Norton trial like i used to, i would highly recommend trying it.