Issue:
-Unable to install EPS6 Client due to error in "Root Certificate Update".

Description:
-Client installation getting failed despite of proper connectivity between Client and Server.

Observation:
-Client Agent Service gets installed successfully.
-Installation process doesn't proceed further.
-Error "Installer setup file is corrupt" occurs while executing the setup file "qhnt64.exe" manually.

Conclusion:
-The client installation was getting failed due to error in "Root Certificate Update".
-Related event logs of certificate error found under Application Event Logs.
    Details: Failed to add certificate to Third-Party Root Certification Authorities store with error: Access is denied.
    Event ID: 4110;    Source: CAPI2

Solution:
-Applied the certificate "MicCerTruLisPCA_2009-04-02" (By Right Click and Install Certificate)
-Client successfully got installed on system.

Source:
http://www.microsoft.com/pki/certs/MicCerTruLisPCA_2009-04-02.crt