This may lead to loss of functionality and/or system instability,[3][4][5] As well as application compatibility updates from Microsoft to block problematic Registry cleaners.
The rogue security software "WinFixer" including Registry cleaners has been ranked as one of the most prevalent pieces of malware currently in circulation.
[11] Rogue Registry cleaners are often marketed with alarmist advertisements that falsely claim to have reanalysed your PC, displaying bogus warnings to take "corrective" action; hence the descriptive label "scareware".
In October 2008, Microsoft and the Washington attorney general filed a lawsuit against two Texas firms, Branch Software and Alpha Red, producers of the "Registry Cleaner XP" scareware.
[12] The lawsuit alleges that the company sent incessant pop-ups resembling system warnings to consumers' personal computers stating "CRITICAL ERROR MESSAGE!
However, this is less of an issue with NT-based operating systems (including Windows XP and Vista), due to a different on-disk structure of the Registry, improved memory management, and indexing.
[13] Furthermore, versions of Windows prior to Server 2003 may fail to start up if the Registry and kernel files are unable to fit within the first 16 MB of memory.
[19] Complications of detailed interactions of real-mode with virtual also leaves the potential for incorrect removal of shortcuts and Registry entries that point to "disappeared" files, and consequent confusion by the user of cleaner products.