The agents are not 32 or 64 bit. The agent like sql agent,exchange agent, hyper v agent are just the licenses that got installed on the media server.As you want to backup exchange 2010 you have to use BE 2010 * 64 bit server to install media server. Also the installation CD of BE 2010 is around 3gb and automatically detects the 32 or 64 bit and installs it. So make sure you check before installing. Also make sure you have install the remote agent to backup the remote server. On all the remote servers that needs to be backed up should have the remote agent installed.
Thanks for your response. Do you mean I should install media server on windows server 2008/2003 64 bit when backing up Exchange 2010? are there problem when I also backup fileserver or sql server on windows server 32 bit to media server 64 bit?
Let's not forget, the Microsoft ecosystem is moving towards 64bit only. So might as well do it now, rather than bring up a new application and realize the ancillary services do not support it... e.g. Exch 2007/2010 on 64bit needs 64bit windows for BE12.5/2010