Windows File Protection (WFP) is a feature of Windows Me, 2000, XP and later, designed to protect essential system files from modification, replacement, or removal. The idea is that system stability will be improved if updates to protected system files are only made through Microsoft-approved means, namely Windows Update, Service Packs, or HotFixes.
In order to achieve this goal, Windows monitors changes to files on the protected files list and automatically restores files that were inadvertently replaced, modified, or removed.
A well-behaved installation program can query Windows to find out if a file it needs to install is on the protected file list. If it is, it should not try to replace the file (which would fail anyway). Optionally, it may alert the customer that the file needs replacing through a Service Pack or similar update, although this is not always appropriate.
Tarma QuickInstall complies with the guidelines laid down for Windows File protection and queries WFP for each file that needs to be installed or updated to find out if it is protected. If it is, no installation attempt is made and the file is silently marked as being successfully installed. All further file-related actions (reference count updates, file registration) then take place as per usual.
Note that the protection check takes place only if the other Installation File Settings indicate that the file must indeed be installed; in particular, the protection check takes place after any platform, language and version checks. If any of the prior checks indicate that the file need not be installed or updated, no WFP query is necessary.
Removal is dealt with similarly: Tarma QuickInstall queries WFP before trying to remove a file during uninstallation (subject to the usual removal checks, such as reference counts) and only removes the file if it is not protected.