Performing a system restore for Windows 8 should only take between 30 and 45 minutes. It takes this long because the restore program checks all types of system files on all paths; in other words, your computer monitors everything during this process.
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If the Restore Is Taking too Long
If the restore is taking longer than 45 minutes, the program is probably frozen. This most likely means that your virus protection program is preventing the restore program from running completely. If this is the case, a window with this message appears: "System Restore did not complete successfully. Your computer's system files and settings were not changed. Details: System Restore could not access a file. This is probably because an anti-virus program is running on the computer…." In this case, you need to use another method to bypass your virus protection and restore your system.