Root Bug Hits Windows 7; Microsoft Advises Reinstall

Microsoft has issued a hotfix for a security permissions bug that can affect the root folder under the Windows 7 release candidate released last week. Microsoft also recommends that affected users reinstall the Windows 7 operating system.

Only the 32-bit versions of Windows 7 Release Candidate Ultimate (Build 7100) are affected, Microsoft said.

Microsoft's Knowledge Base article 970789 details the problem, described as an issue with the root folder of the system drive. That root folder contains incorrect access control lists.

"One effect of this problem is that standard users such as non-administrators cannot perform all operations to subfolders that are created directly under the root," the article states. "Therefore, applications that reference folders under the root may not install successfully or may not uninstall successfully. Additionally, operations or applications that reference these folders may fail. "For example, if a folder is created under the root of the system drive from an elevated command prompt, this folder will not correctly inherit permissions from the root of the drive," the article adds. "Therefore, some specific operations, such as deleting the folder, will fail when they are performed from a non-elevated command prompt.

In turn, users will receive an "access is denied" error.

The fix is available via Windows Update, which will push a Cleanwin7rcroot.exe version 6.1.7100.15 tool to a user's PC.

But to "make sure that this update does not affect your user experience," Microsoft recommends reinstalling Windows 7 from a clean, formatted partition, then immediately running the Cleanwin7 tool, apparently because the newly created folder do not inherit the proper security descriptors. Even after the tool is run, Microsoft says, the permissions/descriptors will not be propagated to any subdirectories.

The Knowledge Base story was first reported by ZDNet.