ctor.dll is a potentially unwanted file, which can be related to various programs. According to computer experts, this file is usually created by Error Doctor 2007. However, it can also be added to your PC system by legitimate programs. If machine gets infected with Error Doctor 2007, its owner should notice tons of annoying ads that typically report about various PC issues. This program can try to make you think that your PC is infected and that you should purchase its licensed version, which in reality, is another virus. That's why you should ignore all ads that are displayed by Error Doctor 2007.
Once malicious version of ctor.dll is installed on computer, it is used for implementing the main functions of the parasite. This file usually needs to be loaded by executables because it can't work on its own. However, some threats inject ctor.dll in the system and reconfigure it from working as an independent component. If that is the case, ctor.dll becomes as web browser plugin that can easily track people's browsing and collect information about their mostly visited sites, data that is entered on them, etc.
As we have mentioned in first paragraph, ctor.dll can be related to malicious and legitimate applications. That's why we highly recommend checking this file carefully before deleting it. You can do that with RegCure Pro.