Backup entire QCS folder, then run repair of the product from the control panel or locate the installation CD and the QCS msi file, then use the following command line to install:
msiexec /i "QCS.3.7.0.msi" /l*v install.log ACSCOPYFILES="YES"
You may need to copy back the content of the Storage folder and acpolicykey.apk from the backup following the installation in case of configuration loss during the repair