Re: GW2 not start
You still have the MSVCR120.dll errors?
You may try uninstalling all the redist packages in Control Panel -> Uninstall.
Then reinstall them.
This is an old 3rd party tool that is no longer being updated/supported... but it still goes up to 2013 (it does the above just easier)
http://mcripblog.cesidian.info/2013/11/vc-redist-installer-160.html
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You may try SFC /Scannow
https://support.microsoft.com/en-us/kb/929833
If it's windows 10 you can also try dism
http://www.windowscentral.com/how-use-dism-command-line-utility-repair-windows-10-image
DISM /Online /Cleanup-Image /RestoreHealth
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Windows 10 offers a "reset" option that allows you to revert windows to basically a clean install state but not remove data files (it does break installed programs so those need reinstalled but data is left intact).
http://windows.microsoft.com/en-us/windows-10/windows-10-recovery-options
That is a sure fire way to fix Visual Studio Redist problems. For older windows just reinstalling (backup first).