Installation of Live Communication Server does halts

I’m having a hard time installing Live Communication Server 2005 on my SBS 2003 machine which contains SQL 2005. The installation process stops when I’m on the part of installing the SQL desktop engine.
I had a trial run for the tree and forest. But again, the installation freezes every time I tick the related link to put in the server files.
Can someone please help me?
Any suggestion is welcome. Thank you so much!
