exchange binary files are not installed but backup settings registry key is present only build-to-build upgrade mode is available

hi - i recently upgraded our exchange server from 2003 to 2007. since then i have not been able to backup mailboxes using our backup exec 12.5. now working through this article (http://seer.entsupport.symantec.com/docs/311718.htm) i have identified that the microsoft exchange management tools (ese.dll) version is different on the exchange and backup server. i tried upgrading the version on the backup server but the upgrade hung and crashed. now for some reason there is no management tools on the backup server and when i try to do an install i get the error -

exchange binary files are not installed but backup settings registry key is present only build-to-build upgrade mode is available

i have tried a complete uninstall of exchange from the command line on the backup server but it says it is not installed.

i have also followed the steps in this article - http://technet.microsoft.com/en-us/library/dd285501(EXCHG.80).aspx but this does not work for me either.

have also looked at this doc http://seer.entsupport.symantec.com/docs/306830.htm but it does not apply as the information stores are the only things being backed up.

the exchange server is 2007 sp2 running on windows server 2008 ent sp2. backup exec is 12.5 sp1 running on windows server 2003 ent sp2.

if anyone has experience with this error message and can assist me with reinstalling the latest version of exchange 2007 management tools on our backup server i would be very grateful.

i have nightly backup server images of the exchange server but need to get this working as would prefer to ba able to restore emails or mailboxes instead of whole server.

if you need any further info on errors or environment please let me know

cheers

rory