Hi Veritas users, here are a few things I have leant whilst doing this BE8.6~9.0

If you have a problem upgrading or even deleting the Remote Agent then rename
the Veritas folder to 'Veritas.old' then try again to remove it.
If you are using a NAS Box then create new folders, if this fails still then
create a mapped drive fooling BE9.0 that it is a local backup
Remove the backing up of all 'system folders' in Exchange 5.5

Another thing you can do is before you upgrade delete BE8.6 but choose the
option to keep the log files then install a new full version of BE9.0

Make sure you reboot after every installation.