If you are interested in starting to explore the Windows Phone 7 development environment, and you also want to use Visual Studio 2010 RTM, please take a look at this post by Charlie Kindel BEFORE you install either set of bits.

Read the whole post for details, but the bottom line is that the Windows Phone Developer Tools CTP released last month is NOT compatible with the RTM release of Visual Studio 2010, so if you install VS2010 RTM on a machine where you’ve already installed the Windows Phone Developer Tools CTP, you will not be able to build your Windows Phone projects.

An updated release of the WPDT CTP should be available in a few weeks to address compatibility. In the meantime, you can either install these bits on separate machines, or use a VM for the RTM release of Visual Studio 2010 (running the WPTD on a VM is not supported).