These are usually anti-spyware or security software applications that use various forms of deception and/or unethical means or show a history of negligent false positives to goad the end user to make a purchase.
In some cases these applications maybe downloaded with some form of unwanted software at which point the rogue application is offered to the customer as a way to remove the unwanted software.
Typically installed though exploits and bundled with spyware/malware, Winfixer scans automatically after installation and reports errors of broken links, registry problems and other errors - even on a clean install of Windows. You have to register the product in order to discover what the errors actually are. Winfixer reports details are vague.
Winfixer also communicates with a tracking server for tracking its affiliate program.