Today at my company I was installing TMG 2010 on Windows 2008 R2 64bit on MS Hyper-visor VM and encounter following errors during installation related to SQL 2008 ,
Example:
# Forefront TMG Installation terminates – SQL Express 2008 Could Not Be Installed
# Error installing TMG 2010: failed to install SQL Express 2008 (reporting instance)
After some googling, I managed to resolved this problem. This is what I did:
# Go to Control Panel > Uninstall Programs
# Uninstall Microsoft SQL Server 2008
# Uninstall Microsoft SQL Server 2008 Native Client
# Go to C:\Program Files
# Delete folders ‘Microsoft Forefront Threat Management Gateway‘ and ‘Microsoft SQL Server’
# Go to C:\Program Files (x86)
# Delete folders ‘Microsoft SQL Server’
# Reboot your windows
# Right click on TMG Setup and select ‘Run as Administrator‘ , and follow on the screen setup.
This time installation went smooth.
After this I installed TMG SP1 and SUP1 from
You can download SP1 from : http://www.microsoft.com/downloads/en/details.aspx?displaylang=en&FamilyID=f0fd5770-7360-4916-a5be-a88a0fd76c7c
and you can download SU1 from : http://www.microsoft.com/downloads/en/details.aspx?FamilyID=695d0709-0d8b-45ee-afdb-727c4428ca4d
Afterwards, download TMG SP2 , and install it.
http://www.microsoft.com/download/en/details.aspx?id=27603
I hope these steps will help you too 
I will write more soon.
Regard’s
Syed Jahanzaib
