PowerShell 2.0 comes with R2 but not Windows 2008 SP2 so that I need to install Active Directory Web Services (ADWS) first. I went to this MS
download page, and tried to install "Windows6.0-KB9868934-x86.msu but failed with "The update does not apply to your system".
Googled and found out that I need to install this patch first mentioned in this
KB article.
Notes: after done this, I still cannot run AD module on my Windows 2008 SP2 server. Based on this
article, I need to use Windows 7 or Win08 R2 to manage it.