Accessing files contained in the Global Assembly Cache

If you plan on writing any custom code against a SharePoint site, the first thing you're going to need to get your hands on are the SharePoint assembly files that are installed in the GAC (Global Assembly Cache).  Here are the steps to obtain such files:

1. Log on to the SharePoint web front end server
2. Open a DOS command prompt (Click Start -> Run, type "cmd", and hit Enter)
3. Type "subst G: %windir%\assembly"
4. Open Windows Explorer and navigate to the newly created G: drive
5. At this point, you have direct access to the .dll files stored in the GAC and you simply have to drill down the folder structures to find what you're looking for

P.S.  If you're looking for Microsoft.SharePoint.dll, it's located under the GAC_MSIL directory...