Beside using Windows Phone SDK to test the windows phone apps - xap files (those without source code), are there other ways (or alternatives or emulator) that I can use to test the xap files?
take a look at this forum might help How to transfer .xap file to Windows phone ?
Extract from the link given above:
Using a custom ROM after using WindowBreak to transfer xap files to Windows phone.
Quote from engadget
So one way would be to create a a company account and distribute the xap file that way. You can download the required app at Microsoft. There are some prerequisites like System Center, so it is not feasible for an individual.