1. Make sure TMG is installed on a Domain member 2. Make sure TMG beta 2 is installed only on Windows server 2008 and not on R2 ( post beta 2 builds will work on r2) 3. Make sure you have a clean OS and not on the same machine where you had an earlier build of TMG
After all these , if you still have problem Send me the setup logs from the Windows\temp folder
Thank you for your responce. I have already solved the problem. I wanted to post it, but forgot to.
I have Windows Server 2008, no R2. I have already installed TMG Beta 1 before. To solve this problem Before installing again I added ADAM (AD LS) as a feature. After that I was able to install TMG Server 2010 Beta 2.