"Last known-good" restores the last system Registry hive (containing driver and service configuration) that successfully booted the system. Malware removal These tools are also difficult to manage in a non-boot situation, or during an infestation, compared to a full system restore from a backup. In the age of rapidly evolving malware, even a full system restore may be unable to remove a rootkit from a hard drive. Registry cleaners are likewise not designed for malware removal, although minor side-effects can be repaired, such as a turned-off System Restore. However, in complex scenarios where malware such as spyware, adware, and viruses are involved, the removal of system-critical files may result. Application virtualization A Registry cleaner is of no use for cleaning Registry entries associated with a virtualised application since all Registry entries in this scenario are written to an application-specific virtual Registry instead of the real one. 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. There is little competent information about this specific interaction, and no integration. In general, even if Registry cleaners could be arguably considered safe in a normal end-user environment, they should be avoided in an application virtualization environment. See also Utility software References Utility software types Windows-only software Rogue software Scareware