Playing with the emulator:
The WP7 emulator actually does a lot more than just run your games from VS 2010. If you want to make use of some of the “hidden” features of the emulator, you need to run it separately from VS 2010 and use some of the command line options.
If you open up a command line window and navigate to C:\Program Files (x86)\Microsoft XDE\1.0 you will find a program called XDE.exe.
Run that and you will get the this popup showing the available Command Line Options.
This by itself is not enough to run the emulator though. You need to provide a path to the ROM, which is located in a different folder. To just get the basic emulator running from the command line, you need to point it at a file called WM70C1.bin.
As of the most recent beta of XNA 4.0, you can find the ROM file in this location: c:\program files (x86)\Microsoft SDKs\WindowsPhone\v7.0\Emulation\Images\WM70C1.bin
Starting the emulator is as simple as providing this path, like so:
xde.exe “c:\program files (x86)\Microsoft SDKs\WindowsPhone\v7.0\Emulation\Images\WM70C1.bin”
Make sure you run XDE from it’s home folder and use the double quotes or your path won’t resolve properly.
At this point you should have the emulator up and running.
If you take a look at some of the options, you can see some pretty interesting stuff like loading different skin files, emulating RAM size, simulating battery power and emulating the internal flash memory (and saving it out to disk)
Try a few and see what you think.
At some point, instead of dropping out to a command line, you may want to make a more permanent shortcut. You can either create a batch file in notepad that handles changing directories and running XDE with the proper parameters, or you can create a Shortcut that does the same thing. Either of these options will allow you to tweak the command line options you pass into the emulator.