UPDATE: There is now a patch 3 out so be sure to use this. You can download the patch here Here is a step-by-step guide for upgrading Veeam 6.1 to 6.5. I have seen some post on the veeam forum regarding upgrading SQL 2005 express (standard in 6.1) to a newer version that is supported by Veaam B&R 6.5 this is not necessary, the installer will upgrade the SQL to the version used with Veeam R&B 6.5.
Download the latest installer from Veeam’s home page and run the .exe. The installer will check for prerequisites and prompt for installation and reboot if necessary.
Next the Veeam B&R installer will detect the older version and ask if you would like to upgrade, click ‘yes’
A welcome- and EULA screen will show, click ‘next’ and ‘next’