Richard does a great series of 4 posts on the Global Assembly Cache (GAC) in CLR 2.0..more than you need to know for sure!

 

The Wonders of the Whidbey GAC -- Part I: Processor Architecture

The Wonders of the Whidbey GAC -- Part II: Interop with the Everett GAC

The Wonders of the Whidbey GAC -- Part III: Binding Order Among the v1.x, v2.0 MSIL and v2.0 Bitness GACs

The Wonders of the Whidbey GAC -- Part IV: Shipping Everett and Whidbey Versions of the Same Code

 

Enjoy!