when I download the file Update for Windows Server 2008 R2 x64 Edition (KB2775511) I get two files one is

AMD64-all-windows6.1-kb2775511-v2-x64_ec18cc10e27faf443c17e7a8073c9eba773eb13e.msu

AMD64-all-mpsyschk_01f93e9ed9d1a3e15fd42503dc5ef43dd333670e.exe

what does second file does?

Hi,

In my opinion, maybe its a requisite file while installing the hotfix. If you download the hotfix from the official webpage, please just keep it while installing it.

Here is the webpage of the hotfix, please refer to it before installing the hotfix.

An enterprise hotfix rollup is available for Windows 7 SP1 and Windows Server 2008 R2 SP1

http://support.microsoft.com/kb/2775511

Regards,

Andy Qi