Problem with windowscodecs.dll

hi guys.
a few days ago a problem appeared when i tried running Visual Studio 2010. a startup crash when i tried to open Visual Studio and the cause of crash was windowscodecs.dll

i thought something is wrong with the licence file or visual studio is corrupted and etc. i searched over the net but didn't find anything about it.

i tried reinstalling visual studio but it didn't helped. so i restored my windows using driveimage xml to an old backup. unfortunately even after the restore i got same crash error.
after that i was really hopeless i searched again and found some tutorials about sfc /scannow command.
i runed it and it says unable to fix. i didn't ask for any install dvd. i restarted pc. windows did some configure stuff at shutdown and at logon. but the problem didn't solved.

so i manually replaced the windowscodecs.dll in safe mode using the install.wim
then the crash error is now gone and i can open visual studio 2010.

there are somethings that are not clear to me:
1. after i restored the system to an old backup, how is that possible the problem with windowscodecs.dll appeared again in the backup state ?
2. we have to run sfc /scannow a few times to get it working, right? i run it for 3-4 times but each time it says unable to fix. is something wrong ?

there is also a file called sfcdetails.txt after i opened it i found all lines are reporting about this :
Cannot repair member file [l:34{17}]"WindowsCodecs.dll"

can you guys help me repair the corrupted files ? and please don't ask for a clean install or reinstall because i have lots of data and apps on my laptop and can't do that.