sender.html definition, relationships, removal:

PC Activity Monitor malicious parasite that violates user privacy and damages the compromised system. The sender.html file can be used for different purposes depending on the related parasite's type, functionality and carried payload. Although sender.html may not take any malicious actions by itself, it ensures that a parasite is working properly and therefore needs to be removed. DO NOT open, execute or edit sender.html!
The sender.html file is installed and used by keylogger PC Activity Monitor.
In some cases a presence of sender.html does not mean that your system is infected. The file may actually belong to some fully legitimate applications and therefore must stay intact. If you are in doubt, please scan the sender.html file using you regular spyware remover or antivirus program.