Troj_Dloader.OW is a Trojan that is downloaded from remote sites by other malware. It can also be downloaded unknowingly by a user when visiting malicious Web sites.

The message poses as a reminder to an update for a legitimate application. Clicking the OK button triggers this Trojan's download routine.

It terminates certain processes, if found running in memory.

It displays the icon of files related to certain applications, which further tricks a user into thinking that it is a legitimate file.

It accesses Web sites to download possibly malicious files. As a result, routines of the downloaded files may also be exhibited on the affected system.

Technical details can be found at this Trend Micro page.