Segue uma dica bem legal para fazer a instalação independente do MOM Reporting:

Installing MOM 2005 and MOM Reporting on SQL 2005

OK, I have now completed this and have figured out the procedure. Firstly, you will need the SP1 slipstream copy of MOM 2005.

- Install SQL 2005 and Reporting Services 2005
- Install MOM 2005, no issues here
- Apply the 2 MOM hotfixes (KB913801 and KB913812)
- Install MOM Reporting using the following run command:
       msiexec /i <path>\MOMReporting.msi PREREQ_COMPLETED=1

- IMPORTANT - At the virtual directory selection screen in the MOM Reporting setup, uncheck the automatic box and enter 'ReportServer' in the 1st box and 'Reports' in the second (by default). You will then be able to continue on through the setup.

- Install the final hotfix (KB915785)

Fonte: http://myitforum.com/cs2/blogs/adominey/archive/2006/04/06/19671.aspx

[ ]’s
Jamal Ibrahim