Antivirus Sentry (AntivirusSentry), just like strong majority of fake virus removers, is a virus itself to certain extent. It likes to use a backdoor of your PC to upload and install its trial that with trojan; spamming and exploits of some web-sites are also widely applied methods of  AntiVirus Sentry installation, though you can [...]

Source: http://hands-oncorp.com/2008/10/29/antivirus-sentry-antivirussentry-removal-instructions/