XPAntiVirus is a rogue antivirus software that, when runs, display false results as a tactic to scare you into purchasing the software. When XPAntivirus is first installed it will create 9 entries in your Windows Registry that impersonate infections on your machine. In reality, though, these registry entries are harmless and have absolutely no effect on your computer. Instead, these entries are set so that XP AntiVirus can find them when scanning your computer and report them as infections. In order to remove these fake infections you need to purchase the software as the trial does not allow you to remove them.
As you can see this program is fraudware in that makes changes on your computer and then states these changes are infections as a scare tactic to have you purchase the software. It goes without saying that under no circumstances should you buy it. The program does come with a removal option in the computer's Add or Remove Programs list, but when you attempt to uninstall it, all that happens is the entry is removed from the list and program's process is terminated. Next time you reboot, XP AntiVirus will start up again.