Having recently got myself set up on a 64-bit development environment, I have found myself coming across this problem when you want to make a SharePoint workflow project in Visual Studio. If you try to create one of the SharePoint workflow projects you will get this error message - "A 32-bit version of SharePoint Server is not installed. Please install a 32-bit version of SharePoint Server".

This is a know issue and Microsoft are apparently working on it, but in the mean time here is a nice way around it. If you have the WSPBuilder extension for Visual Studio installed (www.codeplex.com/wspbuilder) just use the project template it provides for a WSP Builder project and you can then add workflows to your project.

The other bonus of this is that you still get all the cool features of WSP Builder in Visual Studio, so it will set up a feature for you, and you get the easy deployment of the WSP file for testing etc. In my opinion this is a better way to doing it than the normal Visual Studio Template, but it will certainly get you around the 64-bit issue.