A side note: If you install, and you see an error message during the install (When I installed, I did have this error message), then you will need this info. Here is the fix:
Close the Install that failed, right click on the Executable for Windows Live Mail Desktop Beta, and choose “Extract.." . Then once it has extracted launch only the .MSI file
Another way to fix the same problem ,
Go to your main drive (typically this will be the C drive), then into Documents and Settings, then your username, then Local Settings ** then Temp, then delete everything in this folder. Then relaunch the EXE file for Windows Live Mail Desktop Beta. (**Note you will need to enable hidden files and folders to be able to access the Local Settings Folder)
For more information on Windows Live Mail Desktop Beta, and/or to join the beta and download a copy...