I just installed a new virtual machine with Windows 7 Enterprise. As I wanted to have some good protection from viruses and malware, I decided to go for Forefront Client Security.

I copied the installation files for FCS to a local temp folder, and executed the command CLIENTSETUP.EXE /NOMOM (to install FCS with the MOM agent). Keep in mind that if you are using a x64 system, execute the clientsetup.exe inside the x64 folder
This installation failed because of UAC.
I changed my UAC settings to low by launching the “Change UAC Settings”, under the tool tab in MSConfig.

Again I tried to execute the CLIENTSETUP.EXE /NOMOM.
This time FCS installed correctly.
After installation I pressed the “Check for Updates Now” inside FCS, but it reported that there we’re now updates….strange, because the definition files are from September 14th 2006.

I then found this webpage: http://support.microsoft.com/kb/935934/ you can download the antimalware definition files manually and install them. This solved it for me.