Damages to registry database caused by registry cleaner:

A problem associated with registry cleaners is that some of them do not rate the severity of errors, and most that are able to do this incorrectly classify errors as critical, with diminutive reasons in support - a contemporary form of snake oil.

Discover the disadvantages using Registry Cleaners:

Critics question the validity of Registry Cleaners on the ground that there is no reliable method of assessing whether the third party application contains redundant information, invalid key or not.

Inefficient and poorly crafted Registry Cleaners could not make distinction between used and unused key for Windows. It could not assess the detrimental effects of removing used key from computer.

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This has given rise to instances like system instability and/or loss of functionality, and subsequently, the release of application compatibility updates by Microsoft for blocking the registry cleaners causing problems.

Registry Cleaners have their own limitations for instance they cannot correct scenarios like undeletable registry keys owing to insertion of null characters in their names. Some specialized tools such as Sysinternals (now Microsoft) and RegDelNull utility can perform this task.

Recovery Power:

Registry Cleaner could not repair those Registry hives which couldnt be mounted by the system.

Despite all these problems, a corrupt registry can be recovered in several ways supported by Microsoft. For instance Automated System Recovery by using System Restore or by running setup from the Last Known Good boot menu.

Removal of Malware:

Despite all these problems, a corrupt registry can be recovered in several ways supported by Microsoft. For instance Automated System Recovery by using System Restore or by running setup from the Last Known Good boot menu.

Registry cleaners are unable to sense or flush out registry entries related to a rootkit that tends to conceal this fact from other procedures.

A specialized tool is needed to compare the results of Registry APIs with the raw underlying Registry storage.

Do Registry Cleaners work in application virtualization scenario?

Registry Cleaners prove inefficient in case of virtualized application because all the Registry entries are written for virtual Registry. This virtual Registry is specifically designed for a virtual application instead of real one.