Is there a Coding Standard document available for download from Microsoft ? I want to use their standards, mainly for C#.
If you wants guidelines published by Microsoft, google them or use links in other answers.
But if you want "standards used in Microsoft's own code" - there isn't a single answer. Microsoft is a big company with many divisions and acquired code, so each project or product has it's own style.
Even style of .NET Framework itself is slightly different from what StyleCop suggests.
My point is, paying more attention to those guidelines and white papers than Microsoft itself does might be not be a good idea.
If you're using C#, you can learn Microsoft's preferred style as you code by running StyleCop on any code that you write. It's a lot easier to learn that way than trying to absorb some huge document.
The patterns & practices Guidance Explorer
"is a tool that enables discovery, composition and consumption of high quality development guidance. Guidance Explorer installs with a connection to the patterns & practices guidance library including performance and security topics for .NET, ASP.NET, and ADO.NET applications. The guidance library contains a variety of guidance types including checklists and guidelines covering design, implementation and deployment topics."
So, this will be a bit friendlier than one big document and will let you:
alt text http://i3.codeplex.com/Project/Download/FileDownload.aspx?ProjectName=guidanceExplorer&DownloadId=25389
Also look at Microsoft Developer Center: Patterns and Practices, though some of that is more high-level than just coding standards.
MSDN is a great place to start a search for anything related to programming on Windows. You can start with:
Remember there is no one size that fits all and conventions/standards change from team-to-team, language being used etc.
Design Guidelines for Class Library Developers
Naming Guidelines