The procedure did not passed throught, so I decided to ripoff the previous installation (fresh backup data available) and reinstall, however downloaded file pulled through installation but the service could not start.
I saved the content of C:\ProgramData\Veeam\Setup\Temp if needed.
Before trying to reinstall, I removed all the files from C:\ProgramData\Veeam of the previous installation with attempted updated (saved in separated folder), the content of the HKEY_LOCAL_MACHINE\SOFTWARE\Veeam registry key.
Install seems to have mostly passed through, but service do not start up.
On this computer is installed Norton 360 fully updated at present day (26.3.10886 (build 26.3.10886.973)) which is not my usual bread and butter but still installed here and worked nice with Veeam Agent until 6.3.2. Smart firewall function enabled
Computer backup is made via through USB drive, no network use and no necessity to use network.
Again: database/old data is not an issue, ready to wipe everything about Veeam but not to reinstall windows