You want to get a CHM file of all the Silverlight 2 Beta 2 MSDN docs? Get it here. Using this file you don't have to deal with the delay of online browsing and when you do a search, you are only searching in Silverlight content.
Note that these docs are the exact same as the Silverlight docs on MSDN online. Of course this offline CHM will become outdated over time which means you'll have to watch for the next offline CHM to be available.