System File Protection (SFP) is a feature implemented in Windows Me that ensures files critical to system operation are not replaced by older versions or versions not approved by Microsoft. Any product can replace system files only if the file is shipped with a catalog signed by Microsoft that references a newer file version. If a product, including Microsoft products, attempts to replace a Windows Millennium protected file with an older version of a protected file, the files will be automatically replaced with the protected files. If an installer program or user copies over or deletes a core system file, SFP "silently" restores the original version of the file. SFP does not display an error message or any other type of message during this process. It is important to note that SFP cannot be turned off.

SFP maintains a log of all protected files that have been replaced. The log file, Sfplog.txt, is in the Windows\System\SFP folder. If there are any entries in the log file (other than the log entry that is added when Windows first starts), then SFP had to protect some files. This should not affect the functionality of the programs installed on your computer.