AppLocker can't be enforced on Windows 7 Professional (or lower). In my case that was a deal breaker.

http://technet.microsoft.com/en-us/library/ee424382.aspx

That being said a very restrictive Software Restriction Policy as linked below would mitigate CryptoLocker as it exists today. It has worked well for me so far.

http://www.mechbgon.com/srp/