Backup Exec 12.5 with Windows Server 2008 R2 64-bit

Everything I've read says that Backup Exec 12.5 is not compatible with Windows Server 2008 R2 64-bit as a media server.  However, I've run into an installation where 12.5 is installed and working fine on a 2008 R2 media server.  It was previously backing up to tape but is now backing up to disk.  It's even backing up a couple of other servers through the remote agent.  It's running Backup Exec 12.5 with SP4 plus various hotfixes/updates.

I believe this may have been initially installed back when 2008 R2 was very new if that matters.

So, what is the issue with 12.5 running on 2008 R2 media server exactly?  Will it just not install?  Are there functional issues?  If this is installed and seems to be working, should I leave it?

Thanks