What are the registry disadvantages using a registry cleaner?

The biggest disadvantage of Registry Cleaners is their weak distinction feature. Some Registry Cleaners fail to rate severity of errors and those succeeded erroneously categorized errors as critical without giving proper reason of categorization.

What are the disadvantages of Installing 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.

Weakly developed registry cleaners may certainly not identify whether a particular key is still in use by Windows or what dire consequences it may have on being removed.

You can avoid the mentioned disadvantages if you use a proven tool that will ensure you get a fast computer

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.

Capability of Recovery:

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

However, there are several ways supported by Microsoft to repair a corrupt Registry. For example Automated System Recovery feature of Windows XP wherein last Known Good boot menu is achieved by using System Restore or by running setup.

Malware elimination:

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 could not remove Registry entries associated with a rootkit because this rootkit hide the information from other processes.

It is a must for a specialized tool to compare results from raw core registry storage with that given by Registry API.

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.